Klarus GL5

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Klarus GL5 review: gun light test

Klarus GL5 specifications

Brand & ModelKlarus GL5
Lumens1,200 Lumens
Beam intensity18,320 cd 
Battery config.1*18650 / 2*CR123A
Onboard chargingN/A
Review publication dateJuly 2022


When I first got into the deep, deep rabbit hole that is BudgetLightForum, group buys were fairly common. One of my first purchases after joining BLF was from a group buy for the Klarus Mi7 – a AA/14500 side switch light offered in a large array of colors (including the nice silver option that I chose). It was a pretty sweet little light, but I ended up letting it go because of the cool white LED and UI preferences. After that, I haven’t really heard that much about Klarus. I know they’re still around and still producing nice flashlights, but they just don’t seem to be very common on BLF. And honestly, that’s a shame – Klarus really does make some good stuff.

So when the opportunity came around to review the new Klarus GL5, I was legitimately intrigued. The GL5 is a new gun light, but it’s not ordinary gun light – it’s actually what’s called a “forward grip” with an integrated light. That’s another new thing I’ve never tested before and all the more reason for me to be curious about Klarus’ new offering.

Package quality.

The packaging of the Klarus GL5 is nice, but not extravagant. It’s a 2-part heavy paperboard arrangement with a black plastic form-fit tray inside. The carton is mostly white with an image of the GL5 and some key specs listed on the front. In all, the package contained:

  • Klarus GL5
  • Battery (2 * CR123A’s, in the light)
  • Spare o-ring
  • Manual

Flashlight in use

Usually when we talk about how it is to hold the flashlight, it’s because that’s just part of the ergonomics of the light. But with the GL5, that’s actually part of the main function of the tool. You see, when firing long guns (rifles and shotguns), your grip usually puts your non-dominant hand grasping the handguard, forearm, or stock of the gun in a horizontal fashion. This grip is honestly a bit awkward but I’ve been shooting for about 30 years and I’m just used to it. For AR-15 style guns, though, it’s not uncommon to add something called a foregrip or forward grip. This is a vertical handle that attaches to the handguard, providing a much better grip on the gun with your non-dominant hand. The foregrips are frequently basic, inexpensive polymer handles. But there are some fancy ones out there that fold up and away when not in use, or have a bipod that extends out from them. The Klarus GL5 brings a new twist: an integrated tactical gun light.  

The GL5 has a MIL-1913 / Picatinny rail on the top for attaching to the gun. The mount tightens down with a convenient thumb screw. It goes without saying that your gun would need a Picatinny rail in order to use this. That seems like a no-brainer comment, but M-LOK handguards are becoming increasingly popular for a variety of reasons. A common complaint against the quad-Picatinny handguard is that they’re a cheese grater and can be a bit rough whereas M-LOK is much more comfortable to hold. So just know that if you’re running an M-LOK handguard, you’ll need a Picatinny adapter.

The back of the GL5 has two buttons that are logically positioned where your thumb should sit when using the foregrip. The smaller left button is an e-switch that activates Strobe mode. The larger right button is a clicky switch that activates the constant-on modes.

Build Quality, and Warranty

The head of the Klarus GL5 is made of hard-anodized aluminum with a satin black finish. Most of the surfaces are flat and smooth, with the exception being the bezel which has some large blocks machined around the circumference. The handle itself is a thick piece of rubber that is very grippy and easy to hold onto.

The tailcap is a stout piece of aluminum with reeding cut around it. The threads are square cut and smooth, non-anodized. The cap is simple to remove and reinstall and should be easy to do so even with gloves on.


  • Klarus guarantees against defects in material and workmanship for 5 years from the purchase date, the light would be repaired or replaced without charge.
  • Rechargeable batteries are covered by a 1 year warranty
  • Limited Lifetime Warranty: after 5 years, Klarus will charge for parts and repairs

LED, Lens, Bezel, Beam, and Reflector

The bezel of the Klarus GL5 has some fairly aggressive crenelations. I’m not really sure why that’s necessary, but I suppose if your life depended on it, you could wield the GL5 like an aggressive hammer?

Inside the bezel you’ll find a sheet of glass covering the smooth reflector. Nicely centered in the middle of that smooth reflector is a Cree XP-L2 HD V6 LED. In general, that’s a fairly bright and efficient LED, at least as far as 3 volt emitters go. But… being one of Cree’s flip-chip designs in a smooth reflector, there is of course some of the Cree rainbow (tint shift) throughout the beam. And also as expected, since this is a tactical-centered light and not something catered towards EDC enthusiasts, we’ve got a standard-CRI cool-white LED. Measurements from the Opple Light Master are:

  • CCT: 7120K
  • CRI: 72.8 Ra
  • DUV: -0.0003

Dimensions and size comparison




Without battery:28610.1
With batteries (Samsung 30Q)33211.7

Weapon mount flashlights comparison

Gun lights, left to right: Olight Valkyrie, Klarus GL5, Olight Baldr S BL

Driver & User Interface:

When it comes to gun lights, less is more. The easier to use and more predictable they can be, the better. So I think Klarus did well on this one. From Off, one button is Strobe and the other is High mode. Nice and easy, right?

Available modes: Low, Medium, High

From OFF:

  • Press and Hold Mode Switch < 2 seconds: momentary Strobe
  • Press and Hold Mode Switch > 2 seconds: constant Strobe
  • Single click Main Switch: turn on in High  

From ON:

  • Press and Hold Mode Switch: Strobe
  • 1 click Mode Switch: change brightness (High > Medium > Low)
  • 1 click Main Switch: turn Off  

Mode memory:

  • No, there is no mode memory. It always turns on in High (which is a good thing)


  • To High: click the Main Switch
  • To Strobe: hold the Mode Switch

Low voltage warning:

  • There is no warning that I could tell, aside from the light being dim


  • There is a Strobe mode, activated by holding the Mode button down

Lock-out mode: 

  • None


  • None, there is no PWM

Additional info on the UI: 

  • Klarus says this light features an Intelligent Thermal Protection System (ITS). When using the GL5 with 18650 batteries, it did a great job of regulating the temperature. Unlike many such algorithms, it both decreased and increased brightness as needed and did so without over-reacting. Unfortunately, it was a different story when using CR123A’s – the output cycled pretty dramatically every minute or so while trying to get the temperature dialed in.

Batteries & Charging

The Klarus GL5 ships with 2 Panasonic CR123A batteries inside. It also accepts a wide variety of 18650 batteries, aided by springs at both ends. I did most of the testing with a flat-top Samsung 30Q battery which is relatively short. I also tried it out with a quite long protected Panasonic NCR18650B with built-in micro-USB charging. The GL5 didn’t complain about any arrangement that I tried. Well, except when I put the batteries in backwards. No damage was done, the light just didn’t turn on.  That’s a pretty easy mistake, as I would consider that the batteries go “the wrong way” with the negative pole going towards the head of the light. If you forget, there’s actually a reminder molded into the rubber of the grip.

My one gripe regarding batteries and the Klarus GL5: there doesn’t appear to be any low-voltage protection. My first runtime test kept chugging along for a long time at under 10 lumens. I finally stopped the test when it got down to 3 lumens. I checked the battery voltage: 2.55 volts. Ouch. During the next test, I pulled the battery at 7 lumens hoping for better: barely, it was sitting at 2.58 volts. So, I’m really glad that the GL5 accepts both protected 18650’s and CR123A’s. I’m not putting any more unprotected 18650’s in the light.

Performance test

Lumen measurements:

For current measurements, an ANENG AN8008 multimeter and UNI-T UT210E clamp meter were used. Lux was measured by a UNI-T UT383 BT at 10 meters. Lumens were measured in a homemade lumen tube using a TSL2591 sensor, calibrated with a Maukka calibration light. Testing was performed with (1) the included Panasonic CR123A’s and a Samsung 30Q.

Lumen measurements (for each mode)

ModeAmps at startSpecs@turn on@30 sec@10 minutes
Low (18650)175 mA100 lm113 lm113 lm112 lm
Medium (18650)1.1 A500 lm594 lm593 lm578 lm
High (18650)3.4 A1200 lm1389 lm1346 lm924 lm
Low (CR123A)100 lm
Medium (CR123A)500 lm
High (CR123A)1000 lm1420 lm1354 lm1034 lm

Parasitic drain:

  • 26 µA

Runtime graph

As I mentioned when talking about the UI, there is thermal regulation going on. It seems to do a really good job with 18650’s.  But on CR123A’s, the output really varied up and down as it tried to settle in.

ModeSpecified runtimeMeasured runtime (ANSI)Time till shut off
Low (18650)13 hr*16 hr 21 min> 18 hr 37 min
Medium (18650)2 hr*2 hr 47 min> 3 hr 51 min
High (18650)1 hr*1 hr 36 min> 4 hr 35 min
Low (CR123A)8 hr
Medium (CR123A)1.2 hr
High (CR123A)40 min1 hr 6 min> 4 hr 33 min

*Note: Klarus’s 18650 runtime spec was measured using a 2600 mAh battery, whereas the Samsung 30Q in these tests is a 3000 mAh battery

ANSI FL1 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.

Throw numbers: Peak beam intensity 

Throw was measured at 10 meters after 30 seconds from turn-on.

ModeSpecsCandela measured MetersYards
High18,320 cd27,500 cd332363

Extra info: Peak beam distance according to ANSI FL1 standards: 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).


Beam shots of the building are taken at 15 m (16 yd) using a Pixel 6 set to ISO 200 with 1/10 second exposure time.

Beam shots of the playset are taken at 30 m (33 yd) using a Pixel 6 set to ISO 200 with 1/2 second exposure time. The trees in the background are around 65 m away.

  • Klarus GL5
  • Rovyvon GL3
  • Wuben T1
  • Nitecore P20i UV

Disclaimer: This flashlight was sent to me for review at no cost by Klarus. I have not been paid to review, nor have I been holding back on problems or defects.

Final Verdict


  1. Solid as a great foregrip should be
  2. Good tactical UI
  3. Accepts a wide array of batteries


  1. No low voltage protection?

Explanation on star ratings:

1: Avoid: my phone flashlight 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

Reviewer Gabriel
Author: Gabriel

4.5 stars: ★★★★⋆

I have reviewed a handful of gun lights over the past few years. For the most part, they’re one trick ponies. That’s not really a bad thing though. When it comes to a gun light, it needs to work the first time, every time. So simplicity is a good thing. The Klarus GL5, though, is a different breed of horse. It’s a foregrip with a built-in gun light. The GL5 is sturdy enough and grippy enough that it could stand on its own as a really solid foregrip. But then Klarus did what Klarus does and baked in a tactical light into the top of the grip. The light itself is really easy to use and has a fitting UI. The only downsides that I can think of is the lack of low voltage protection, but thankfully it accepts the widely-available CR123A batteries as well as protected 18650’s

Buy Klarus GL5 here:

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