Emisar D4K

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Emisar D4K review

Emisar D4k specifications

Brand & ModelEmisar D4k
Flashlight categoryCustom Flashlight / Hotrod / EDC flashlight
LEDCustom mixed LED order* (2)Luminus SST20’s 6500k (1)Osram “W1” (CSLNM1.TG) 6000k (1) w2 Deep Blue *send email after placing order
Max. outputN/A
Max. beam distanceN/A
Max. beam intensityN/A
Battery config.21700
Onboard chargingN/A
Main modesMany custom user-set modes with Anduril
BlinkiesTypical Anduril 2 blinkies (candle, lightning storm, bike, party strobe, tactical strobe, *police strobe)*w/newest Anduril Update 2023-10-31)
Review publication dateMay 2024

Review intro:

Welcome to the wonderful world of custom flashlights! If you have been around the world of flashlights for any amount of time, or have searched beyond what your normal flashlight needs may be, then at some point you will probably come across Intl-outdoor’s “Emisar” brand of flashlights. These lights will take you on a whirlwind journey of led types, color options and custom combinations with features galore. So much so, that it can be quite overwhelming just starting out

The light in this review, to be specific, is the Emisar D4K in a triple channel configuration and houses (4) leds of your choice. The D4K is the successor to the very popular D4v2 (which was an upgrade from the well known D4) by Emisar, but with even more features and a larger battery as well! Sounds pretty great already! With this, new-to-me, “multi-channel” availability in mind and (4) leds to choose from, I selected (2) SST20’s for a good usable flood on one channel, then a single W1 emitter for throw on another. Lastly of course, a third channel. What else but an all blue W2 just for fun! Did I make something amazing? Is this the flashlight of all flashlights? Come along as we take a look into what makes this Emisar D4K Quad LED, a flashlight hotrod that you might want to carry everywhere you go, show off to anyone who will listen and never want to put down!

What’s in the package

Your light will arrive safely in the standard padded manilla packing envelope. Inside that, the not-so-uncommon brown cardboard box. Customized with branding and your order information for which flashlight and led combination you specified, an informational sticker resides on the outside. Inside, a fitted foam insert caresses your custom flashlight while it safely traverses the world to find its way to your doorstep. 

Included in the box you will find:

  • Emisar D4K
  • 2 spare o-rings (typical)
  • lanyard (typical)
  • Stainless steel bezel (ordered extra)
  • deep carry pocket clip (ordered extra)
  • clear optic (ordered extra)

Anything else you may have ordered extra will also be placed securely in this box. Just set up your light for the look and style you like, add your own unprotected 21700 battery and you are ready to start shining!

Flashlight in use, Build Quality, and Warranty

When you first pick up your beautiful new Emisar D4K, you will be surprised at how small it actually feels in the hand. The larger 21700 battery tube does not make this flashlight feel any bigger than many 18650 lights actually are. With a minimalistic approach to body shape and construction, the host has no more “real-estate” than what is needed to do its job of holding all the yummy components a flashlight requires. The finish is smooth but has a slightly textured surface and just feels of quality. A solid feeling without the added bulk that many 21700 sized lights have. The D4K can easily be carried, clipped in a front pocket without any problems feeling heavy or bulky. With fantastic milling and perfect anodized aluminum in the color of your choice, you’re not going to want to put this thing down and we’ve not even turned it on yet!

This light was ordered and then custom built for what I would describe as a custom hotrod that is a lot of fun and can even be used as light-duty, everyday carry special. As previously mentioned, specifically with the multi-channel availability in mind, I thought I could go from a double SST20 for a good usable floody beam, to a single W1 emitter for throw when needing to see out a little further.

Adding that the blue led was just for something new, different and fun in a “custom” flashlight. All of this, not realizing an optic lens with no reflector doesn’t get anywhere near as much throw as I had in mind. The output is more than I expected and not disappointing at all and the (4)led, non-reflector beam is great for the flood-type, general usage I wanted in a carry light. The D4K does heat up quite a bit on the higher output levels. Such a small aluminum host with minimal mass and up to 4 leds running at once would definitely bring the heat. This is even mentioned on the manufacturer’s website.

Being able to change channels and ultimately led combos, is a really neat feature. With the multi-channel driver and Anduril OS, you also have a “tint-ramping” feature, but this was more of an afterthought for my carry needs and usage. The idea there is the ability to “ramp” (think blending, fading light) from one channel to the other. So, ramping from a cold tint to a blue tint only gets really cold, tint-wise. Going from 6500k (sst20) to 6000k (w1) doesn’t have a lot of noticeable change to the eye.

I am now thinking this would have been a better setup with a pair of really warm 519 a’s (like 2700k), mixed with a cooler pair of 519a’s or even the W1’s as they come in around 6000k. A nice warm tint paired with something cold to utilize “ramping” from one to the other would really maximize this tint-ramping feature and allow the user to stop the “ramp” at their preferred tint of led. Still, very cool, different and entertaining to say the least, especially with a blue led in the mix! 

The D4K is manipulated with a white, back-lit, rubber-covered side switch that hides the RGB led combination (other, single colored switches are available). This RGB e-switch is color changeable via the Anduril OS and is very high on the fun/ cool factor. This color also matches the (8) auxiliary leds on the bezel for a very nice, custom look per the user’s choice. A thin profiled, stainless steel ring houses the switch and a “raised” version is offered as well to aid against accidental activation. Both versions give the light a reason not to roll away with this slight protrusion of the body at the switch area towards the head of the light. A perfectly flat tail cap ensures standing ability at the rear end.

Extra tailcaps with or without magnets are also offered on the list of extras as well. All of the caps have a place to use a lanyard if so desired and still will allow tail-standing. I chose the magnetic cap for this light and it holds its own weight very well. No falling issues there. There is no holster offered or specifically available for that matter, but a lanyard is included and a stainless steel pocket clip is also on the list of extras and was ordered for this light. It clips directly over the body tube for a tight, secure fit. I have never had the clip come off inadvertently or at all for that matter. In my opinion, all edc lights need a good pocket clip and this one works well and matches perfectly with the stainless steel bezel addition for an even classier, matching look.

This particular light is CNC machined from aircraft-grade aluminum. I say this particular light, because there are also premium material versions (copper, brass, titanium etc.) available on the website. A smooth, square-checkered pattern on the body tube feels great in the hand and has enough of a texture that it doesn’t feel like it is going to slip away but is in no way irritating or rough. A few, very shallow, heatsinks are milled at the head to help attempt to draw some of the heat away from the business end. This thing produces a lot of heat! The tailcap has vertical cuts around the outside to help with purchase while removing and reinstalling. The nice, big, square-cut threads at each end of the body tube feels of quality and gives great satisfaction as you remove the cap or head to replace the batteries.

There are quite a few available colors depending on what is in stock at the time of purchase. The website will reflect this when you are placing your order. If the color isn’t available, then it will not show up on the drop-down list to choose from. The other colors available for the D4K can include: black, dark gray, cyan, (my version and it’s beautiful), green, red and even a ‘Stone White’ for a small upcharge

The included lanyard is similar to the cheaper style lanyards we all see on budget flashlights, but slightly better in my opinion. As mentioned, there are other ‘extras’ you can add to your order to fully customize your light. Different material bezels, body tubes for certain lights, and the extra tailcap/magnet combos mentioned earlier, just to name a few. Again, I opted for the stainless bezel and pocket clip for this order and was very pleased with the look and feel of this setup. Very classy but colorful and fun at the same time.

For your state of mind when ordering directly from China, there is a product quality guarantee as well as a delivery guarantee from the manufacturer that helps cover you and/ or the product until it arrives in good working order. See excerpt below for the manufacturer’s guarantees directly from the website.

Product Quality Guarantee

1. As a responsible seller, we will select reliable suppliers and fine quality products for our customers.

2. If for some reason the customers get defective products, or there’re quality issues when used properly during the warranty period, we will replace the item within 10 days after the arrival.

3. And repair the items within 3 months without any extra charge.

4. If it’s over 3 months but within 12 months we will only charge the exact cost (non-profitable for us)

Delivery Guarantee:

We guarantee your products will arrive safely in your destination country. In the unlikely event your package is lost, we will re-send the goods or give you a full refund.

LED, Lens, Bezel, Beam, and Reflector

Let the spiral begin! (or continue!) There are many led choices and combinations to choose from when placing your order. A constantly updated drop-down menu informs you of the available leds to select from for each of the specific flashlight models. For the purposes of this review, I am going to use the selected leds in this D4K, which again, is a custom mixed-led order with:

  •  (2) Luminus SST20’s 6500k 
  • Osram “W1” (CSLNM1.TG) 6000k 
  • (1) Osram “W2” Deep Blue

Output is abundant, with a very cold-bluish tint when using all four emitters. This is understandable as one of them is Deep Blue! I generally have selected to carry/ use the flashlight with the (2) sst20’s and the (1) Osram W1, on at the same time just so the tint isn’t so blue. (The UI allows for so much user input here! More on that later in the review). This combination of three leds does put out a good amount of bright, smooth, usable light to say the least, and the W1 adds a little more throw in the mix for an overall slightly brighter experience.

The Carclo 10623 quad optic is installed by default for this version of D4K and is the frosted version. This helps to eliminate any artifacts in the beam patterns, thus creating a nice smooth, flowy light with no hard edges when blasting the darkness. There is a glass lens on top of the Carclo optic, a nice touch. Then there is an o’ring between that lens and the bezel to help maintain a water-tight seal (again, optional bezel materials are also available).

The stainless steel version used in this review was only a few dollars extra to add to my order. The body color matched aluminum bezel that comes standard looks really nice (see photos), but I feel the stainless steel version adds a little more flair, matching the pocket clip very nicely. It also brings a little more durability to your carry-light as it will not show wear and tear near as much as the aluminum version. Under the optic hides an array of 8 beautiful rgb auxiliary LEDs. These are easily one of the best aspects of this custom hotrod flashlight. Every “normie” (non-flashlight enthusiast) that sees these Aux lights lit-up will tell you that your flashlight is on and then they are amazed when you take it out to show them that they always stay on! And of course you are going to want to show it off! Now blast away! Okay, okay, back to the review…. These Aux lights are manipulated with the Anduril operating system and will match the switch with whatever color you set. They can be set on high, low, flashing, or off all together via Anduril os.

When using the (2) SST20’s and W1 together, a large smooth blast of light comes out around 6100k and because it is on the cooler end of the scale, it naturally appears even brighter to the eyes. When using a single W1 or even the single W2 deep blue, the beam lacks intensity but still emits plenty of usable light. The W2 “Deep Blue” is simply beautiful and very rich in color. That was a fun one to take pictures of for the review! Also offered is the clear Carclo 10622 quad optic for more of a spot pattern. This beam does come out a bit squarish which will bother some, but does “throw” the beam a little better if you can stand seeing it. Just unscrew the bezel, (don’t drop your o’ring and glass lens!) to swap out the optic to get to your preferred beam and spill.

Dimensions and its competition


Emisar D4KMillimetersInches
Length103 mm4.1 in
Head diameter26 mm1.1 in
Body diameter25 mm.9 in

Dimensions are rounded to the nearest millimeter and the nearest tenth of an Inch.


Molicel p42a’s were the batteries used for all aspects of this review.

Emisar D4KWeight in gramsWeight in oz
Without battery:78 g2.7 oz
With battery143 g5.1 oz

Weight is rounded to the nearest gram and tenth of an Oz.

Flashlight size comparison with its competition:

Group 2: Olight M2r Pro, Wurkkos TS21, Emisar D4K, Convoy S21a

You can clearly see the size difference with other 21700 cell lights. Being the smallest of the 21700’s shown, the D4K is definitely much easier to carry around and keep clipped in a pocket. 

Group 2: (Emisar/ Noctigon Family photos) – Emisar D1K, Noctigon KR1, Emisar D4K, Noctigon KR4

Within the same family of manufacturers, the white D1K shown here is the only other 21700 shown! Note, the other 2 are 18650 lights and are very comparable in size and carry ability.

Emisar D4K: User Interface and Driver

Very well known in the flashlight community is the Anduril Operating system. It seems people either love it or hate it. Aside from a tactical-use flashlight, I am personally on the love-side and would enjoy all of my lights to have Anduril, just due to the customization abilities. I love being able to set up my light exactly how I want it to work and perform for me and my specific situations.

When you receive your light, it will most likely be in “safe mode”. This is a simpler version of the operating system with fewer available settings. Some might prefer to set this up for a “normie” to use if they have to loan it out and don’t need/ want all the options or if a child was going to use it and you wanted to prevent any burns from a hotrod flashlight.

Okay, now we need a disclaimer: This is not a toy.

But, to make the most of Anduril OS and your Emisar, you will need to get to Advanced mode and prepare to be amazed…or confused. Back to it, you will want to click the e-switch 10 times, holding down the button on the 10th press (10H). Now you can make even more changes to customize your flashlight experience. While we’re here, let’s take a quick look at clicks and holds – say what?!?

A combination of button presses, (aka clicks) and the act of holding down the button, (holds) are used to navigate Anduril and get the most out of your light. Like changing to advanced mode above, there will be a number and letter combo on the Anduril Map of actions.

Download full version of this Anduril 2 Multi Channel image.

-The number is how many times to press the button.

-The letter tells whether to release the final press (C) or keep holding it (H).

(1C) One click. – Press once and then quickly release the button.

(1H) Hold. -Press the button once, but keep holding it.

(2C) Two clicks. – Press and then release quickly, twice.

(2H) Click, hold. – Click two times, but hold the second press.

(3C) Three clicks. – Press and release quickly, three times.

(3H) Click, click, hold. – Click three times, but hold the final press.

(Continues on with larger numbers).

Anduril gives users a choice between a ramping mode or a stepped mode as the main method of light output control. Both are just as they sound. Either ramp up and down to manage your light output or use a user-determined via Anduril, amount of “steps’. There is a user-set limit for the “Low” end of ramp/steps. This will be your moonlight mode and with newer Anduril updates these can be set quite low. There were some early issues with moonlight levels flickering or not working correctly, but I have not had any issues with this in my D4K. (but to be fair, I do update Anduril to the most recent version).

For the “high” end of the ramp, which is referred to as the “ceiling”, users can also set it to their liking. When you get all the way to the ceiling, the light will quickly flash to let you know you are there. I prefer to set my ceiling around 120 just to be able to use a lot of light output with the least heat build up. Then, if I need to, I can easily double click (2C) to get to turbo and bring the sun out.

For purposes of this review, I have programmed the light to be in the stepped mode and to have 7 steps, thus giving us the typical Moonlight/Low/ medium/ high and turbo with a couple of intermediate levels in there as well. The amount of steps is completely customizable with Anduril, allowing steps from 1 to 151!

A convenient feature of Anduril and probably the one I use the most, is the “BatteryCheck”. Three clicks (3C) from Off will start the light to flashing out a sequence of flashes, indicating the current voltage of your battery. This is so nice to have access to anytime you want to know how much charge you have and like I say, it gets used very often. An example: three flashes, a pause and eight flashes will indicate your battery voltage is at 3.8. (The newest Anduril update now flashes out three number places ie; 3.82 – so even more accurate).

There are so many options to customize your user experience with Anduril UI. You will certainly have to spend some time getting around the Anduril map to familiarize yourself with all of the available settings. One last feature I will mention here and something that can get a little complicated for new Anduril users, is the thermal config menu.

Basically, you set what the ambient, resting temperature of the D4K is itself and at what temperature you want the light to start stepping down. A thermal “ceiling” if you will. With the out-of-the-box thermal settings as is, you will notice the output drop pretty quick as these emitters get super hot. (see runtime graphs) This is to prevent the flashlight from overheating and damaging anything. (3C) to get into battery check, then (2C) takes you to the flashing sequence for what the temperature is set at in celsius. (7H) from there gets you into the menu to change both settings. Again, it sounds like a lot but seeing the flow of the Anduril Map will help you get accustomed.

Available modes: 

(Based on 7 steps with Anduril “stepped” ramp style)

  • [Step 1] Moonlight
  • [step 2] Low
  • [step 3] 
  • [step 4] Medium
  • [step 5]
  • [step 6]
  • [step 7] High
  • [Turbo]

Available blinky modes:

  • Lightning
  • Candle
  • Bike Flasher
  • Party Strobe
  • Tactical Strobe
  • Police Strobe*
  • SOS
  • Beacon

From OFF:

  • Press and hold: Starts you at moonlight. (Note, with Anduril, you can set to have the ramp continue up past moonlight or stay at moonlight when holding down the button)
  • Single click: Turns the light ON to the last saved brightness or your “manual memory” preset brightness (Anduril setting) 
  • Double click: (2C) will take you to the ceiling level.
  • Double click and hold (2H) will take you to turbo
  • 3 fast clicks will give you the current status of your battery voltage. It will flash-out the number sequence. For example, it flashes three times then eight times indicating your battery is at 3.8v 
  • 3 clicks then hold (3H) will take you to the strobe menu. (then 2c to cycle thru strobes)
  • 4 fast clicks will put your hotrod into lockout mode. 

(This is a great safety feature to prevent accidental activation.)

From ON:

  • Press and hold takes you straight up the ramp or steps. Getting much brighter!
  • 1 click to turn off
  • Double click will take you all the way to TURBO!
  • 3 fast clicks: will change between stepped and ramped mode for output. 
  • 4 fast clicks will put your hotrod into lockout mode from on or off.

Mode memory:

The Emisar D4k with Anduril OS is equipped with 3 types of brightness memory modes. Automatic, manual or hybrid. With Automatic, the light always uses the last-ramped brightness level. This means it will come on at the same level that you turned off the flashlight. Next up is the “Manual” memory mode. This is where the user sets the preferred level for which the light comes on. So, with the light ON in advanced mode, 10 clicks (10C) will save the brightness level and this level is what output the flashlight will now come on at with one click. Last up is the “hybrid” memory mode on Anduril. This one is a little tough to explain, but can be really useful. It allows the user to set a time in minutes, (up to 140), after which the light will come on at your “Manual” mode’s saved brightness, the one you set. If you turn it on before the hybrid time you set, the flashlight just comes on at whatever level you turned it off.

To try to better explain, if this timer is set to five minutes for example, and you then turn the light off and back on within five minutes the light will come on at the level you turned it off at, not the “Automatic” pre-set one we talked about previously. If the light is turned back on after the five minutes, it will come on at your “Maunal” memory mode, the saved brightness level.

 This is a very handy feature if you are playing with, using your flashlight on a very low mode to walk through your house in the middle of the night, so as not to wake anyone. Then, you turn the flashlight off for whatever reason. If you turn it back on within the five minutes you set, the light will come on at that very low level, not the brighter preset level you set with the 10 clicks. It is a nice feature to give you some time to use the light the way you know and love.

To disable memory mode is as easy as 10 clicks from ON then hold (10h) and after the first flash it’s one more click. It sounds like a lot when reading it but it is way more intuitive with the light in hand and even more so looking at the map!


  • To Low: Press and hold starts you at moonlight. (Note, with Anduril, you can set to have the ramp continue up past moonlight or stay at moonlight – from this press and hold from off action)
  • To Turbo: Double click (2c)
  • To Strobe: three clicks and hold on the 3rd (3h)

Low voltage warning/protection:

  •  LVP: works for all modes (blink, low, and high), at 2.8V 


  • Lightning
  • Candle
  • Bike Flasher
  • Party Strobe
  • Tactical Strobe
  • Police Strobe*
  • SOS
  • Beacon

Clicking three times and holding the button down on the third (3H) from off gets you into the first group of the strobe modes. Then, two clicks (2C) cycles through the strobes list above. The SOS and Beacon are accessible through the battery check path of commands. Three clicks (3C) will take you to the battery check, then two clicks (2C) to temp check, then two clicks (2C) to Beacon, then two more (2C) to SOS etc.

Lock-out mode: 

It doesn’t matter if you have the light on or off, but 4 clicks (4C) of the switch will put your light directly into lockout mode. This is a great way to prevent accidental operation. With the D4K being a side-switch operated light, I haven’t had any issues with accidentally turning it on but this can be useful if throwing it into a bag or purse etc. You can also slightly unscrew the tailcap to manually lock it out if need be.


  • I do not see any PWM

Additional/summary info on the UI: 

  • Anduril is an open-source firmware for flashlights and can be very intimidating at first glance. I feel that if you give it a chance and perhaps it is better to just start looking at changing only the settings you use the most at first. I think you can then expand into further settings once you get the hang of it and it makes more sense with actual in-hand use.
  • If you get too lost trying to set up your light, you can do a “Factory Reset” to reset it back to its original settings. To reset it, first take off the tailcap. Then, hold down the switch when putting the cap back on all the way. Continue to hold the switch down and the light should start a series of flashes that get brighter and faster and then will flash at full power and turn off. You are ready to start fresh with your factory settings in place and in simple mode.

Emisar D4K Charging and batteries

As stated by the manufacturer, only un-protected, flat top, 21700 batteries will work in the D4K. It does not work with a protected battery. For a hotrod type custom flashlight with this kind of output, a good, high capacity, high discharge 21700 cell is the way to go. All testing is done here with fully charged Molicel 21700 P42A 45A Batteries.These cells provide a nominal capacity of 4200mah and a continuous discharge rating (max) of 45A. With the D4K being FET driven, the higher the discharge, the brighter it will be as long as the battery can hold on. FET driven drivers burn off excess voltage thru heat, so use caution when using the D4K as it will certainly get hot at higher outputs! 

Charge typeFitsNo fitAvg. charge time
NoneUnprotected flat top 21700, preferable high discharge rate.Button top, ProtectedN/A

Performance test

Lumen measurements

How Lumens are Measured: Understanding ANSI FL1 Standards How Lumens are Measured: Understanding ANSI FL1 Standards: The ANSI FL1 standards specify that output in lumens should be measured 30 seconds after turning on, as this is the standardized time for measuring brightness according to the industry standard. This is why we focus on this part in our measurements. The ANSI FL1 standards require an ambient temperature of 22 ± 3°C. We record the ambient the ambient temperature to identify potential reasons for any observed discrepancies.

Lumen measurements were taken using my 33cm homemade integrating sphere (IS) and a Dr. Meter LX1330B Digital Illuminance Light Meter, with a 0-200,000 measurement range. The IS has been calibrated using an Olight Warrior X pro and 1lumen.com’s testing as comparable reference sources. The Olight runs for 7 hours at 300 lumens and data gathered was translated into a calibration offset of .067 and then applied to the measured lux from the D4K. All measurements were taken with a fully charged 21700 Moicel p42a 4200 mAh battery and the light was allowed to cool in between measurements.

ModeSpecifiedTurn on30 sec.10 min.
Moon (step 1)not claimed5 lm5 lm5 lm
Low (step 2)not claimed33 lm33 lm33 lm
(step 3)not claimed142 lm139 lm138 lm
Med (step 4)not claimed418 lm411 lm408 lm
(step 5)not claimed956 lm940 lm452 lm
(step 6)not claimed1853 lm1400 lm449 lm
High (step 7)not claimed3089 lm1690 lm307 lm
Turbonot claimed3960 lm1789 lm672 lm

Ambient temperature during testing:

Turbo / High / Medium / Low

  • °C at start 19°C / 19 °C / 19 °C / 19°C /
  • °C at 30 secs 38 °C / 35 °C / 22 °C / 21°C /
  • °C at 10 mins 33 °C / 31 °C / 20 °C / 20°C /

Parasitic drain: (Unable to measure)

Emisar D4K Battery Life: Runtime graphs

How Runtimes are Measured: Understanding ANSI FL1 Standards About ANSI FL1 runtime standards: The runtime is measured until the light drops to 10% of its initial output (30 seconds after turning on). This does not mean that the flashlight is not usable anymore. The last column shows how long the light actually works till it shuts off. If there is a + symbol, it means that the test was stopped at that particular point, but the light was actually still running. This happens on certain occasions, with certain drivers, firmware, or batteries.

Runtimes were measured using the CeillingBounce Android app and a fully charged 21700 Moicel p42a 4200 mAh battery. Max output at 30 seconds for the D4K measured about 1800 lumens. Sadly, this is noticeably half the Turbo output you get at turn on. Emisar does not claim any specific led output or runtimes with this being a custom ordered led-combo. There are some output ratings on the website for certain led selections if all led in the light are of the same type.

ModeSpecifiedRuntime (ANSI FL1)Time till shut off
Moon (step1)not claimedto low5hr 35min+
step 3not claimed4h 15min5h 10min+
step 5not claimed1h 44min2hr 10min
step 6not claimed2h 21min3hr 31min
Turbonot claimed2h 45min2hr 49min

You can clearly see runtimes with factory thermal settings can be visually disappointing “in the long run” (pun intended), but if you know that going in, a hot rod light can be a lot of fun and still useful. Knowing this, I would never run a light like this on turbo for any lengthy amount of time. In a real world application, this really just makes the flashlight too hot to hold without gloves or some form of active cooling (a fan or cold winter air etc.). Generally, just a blast of light if needed (or if showing off!), then set it at a level that meets in the middle of heat/ performance if you need to use it longer.

On most of my Anduril lights I like to set the ceiling at 110-120/151 which allows a bit longer runtime and that itself takes a little more time to get really warm.

Peak beam intensity and beam distance measurements

About Peak beam intensity: Understanding ANSI FL1 Standards About peak beam intensity The calculated value of distance in meters at which the flashlight produces a light intensity of 0.25 lux. (0.25 lux is about the brightness of a full moon shining on an object). This means that the intensity has decreased so much, it becomes difficult to see darker objects, or objects that don’t reflect light. The columns ‘Meters’ and ‘Yards’ use rounded numbers.

Throw measurements were taken outdoors at night in complete darkness at 5 meters using the Dr. Meter LX1330B Digital Illuminance Light Meter. All measurements were taken at 30 seconds with a fully charged 21700 Moicel p42a 4200 mAh battery and the light was allowed to cool in between measurements.

ModeSpecifiedCandela measured MetersYards
Moonlight (1)not claimed22.5 cd9.5 m10 yd
Step (2)not claimed108 cd21 m23 yd
Step (3)not claimed535 cd46 m51 yd
Step (4)not claimed1,640 cd83 m91 yd
Step (5)not claimed3,390 cd117 m128 yd
Step (6)not claimed4,213 cd130 m142 yd
Step (7)not claimed6,080 cd156 m171 yd
Turbonot claimed7,200 cd170 m186 yd

Ambient temperature during testing:

  • 19°C resting temperature 
  • 33°C-35°C for moderate plus usage.
  • 38°C+ when using turbo for more than 60 seconds.

The Emisar D4k custom, hot rod of a flashlight out-performed and under-performed at the same time for me. How is that you ask? Well, I was pleasantly surprised (enough to giggle) when blasting turbo, but soon lost that feeling when trying to use any high-sustained output for any length of time. Within the first minute it gets too hot to hold. Momentary flashes and/ or quick-use scenarios (read: showing off!!!) really does show what makes the D4K a hotrod on Turbo.


Camera settings and distance: 

  • NIKON D3200, 18-55mm VR at  20mm, 1/40 sec., f16, ISO-6400, WB: Auto
  • Distance: 50m to left edge of bridge.

Beamshots of the following flashlights compared:

  • Emisar D4K
  • Convoy S2 plus (Nichia 519A 2700K)
  • Convoy S21B (Osram W1 LED)
  • Sofirn SC18
  • Wurkkos TS21
  • Noctigon Kr1 (Osram W1 6000K)
  • Noctigon KR4 (Nichia 519 mix)

Please note that the following beamshots are mainly intended to showcase the beam pattern and beam quality, rather than overall performance. These images are typically taken directly after activation, and in different seasons or weather conditions, and therefore do not fully represent its overall performance. For accurate performance metrics, such as output, beam distance, and runtimes, you need to look at the performance section of this review.

Disclaimer: we bought this flashlight with our own money. Nobody paid us to review this flashlight, nor have we been holding back on problems or defects. 

Final Verdict


  1. Ergonomics
  2. Value
  3. Customization
  4. Output (albeit short)
  5. Aux LEDs- so pretty!
  6. 21700 larger battery


  1. Gets hot fast on higher modes!
  2. Runtimes are low on higher modes
  3. Can be difficult to order/ knowing all the options.
  4. Cost of some leds/ extras can add up.
  5. You always need another!

Explanation on star ratings:

1: Avoid: a match would be a better choice – 2: Poor: significant defect or issues; almost unusable – 3: Average: some defects or issues; but still usable 4: Good: recommended (minor issues) – 5: Great: highly recommended


4.5 stars: ★★★★★⋆

While our star rating provides a reliable indicator, we encourage you to read the full review to make an informed decision based on your own needs and preferences.

On the forefront of custom hotrod flashlight greatness is the Emisar D4K. It certainly has all of the bells and whistles anyone could want or ask for in a “custom” flashlight. You get to choose the materials used, LEDs you want, the operating setup (highs and lows and everything in between!) and of course all the features and accessories you want to add. You just can’t beat that for a custom personal flashlight experience!

The beautiful auxiliary leds are such a nice look, constantly taking your eyes away from whatever it is you’re doing. All the while fighting your will to not pick up this light and turn it on. I would venture to say that it does perform well enough for an everyday-carry type light, assuming you’re not going to need to blast away for hours in some search and rescue type situation. If that is the case, I would probably grab a different flashlight.

Having said that, I think there can easily be a middle ground setting that any user could find that would give the best output with a longer runtime for consistent daily use. Plus, having almost 4,000 lumens on tap at your fingertips is quite awesome, even if it only lasts less than a minute!

My personal rating for the D4K using a 1-5 star rating:

  • 5 quality/ (really nice anodizing and construction)
  • 5 price/ (not expensive at all for what you get! (Even on-sale usually at manuf. website)
  • 3 performance (the only downfall of the D4k but crazy output just can’t be sustained)
  • 5 features (so many!)
  • 3 upgrades from previous version (not alot to add here except the 21700 battery!)

I would give this light a 4.5 in a custom flashlight category. The only thing bringing it down to this rating would be the sustained output. It probably would’ve been a perfect light, rounding out a 5, if consistent output would have at least been slightly higher.

Buy your Emisar D4K here

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