Cyansky K3 V2

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Cyansky K3 v2 review

Cyansky K3 v2 specifications

Brand & ModelCyansky K3 v2
Flashlight categoryGeneral purpose / tactical flashlight
LEDLuminus SFT-40-W
Max. output2000 lumens
Max. beam distance700 meters
Max. beam intensity124,690 cd 
Battery config.1*21700, 2*CR123A
Onboard chargingNone, but included battery has a USB-C port
Review publication dateNovember 2022


Since Dave reviewed the Cyansky H5 way back in 2021, Cyansky has been busy releasing new lights. I reviewed their K3 tactical light in 2021, and later their HS6R headlamp. Both were decent performers with unique features. The Cyansky K3 in particular was a nice alternative to Fenix’s PD series lights. Well Cyansky is at it again, and we know tactical-style and tactical use (there’s a difference) flashlights are a big deal these days, and with each manufacturer one-upping each other the first edition K3, while still relevant, is showing its age.

Today I’ll be taking a look at the updated K3. It’s still a far-throwing tactical-style light, has a tail switch and e-switch, and retains the nifty glass-breaking nobbles on the bezel. What’s changed? The output has been increased a bit, as has the beam distance (from the added output, no doubt). The side e-switch is also new, and there’s an important functional addition as well. That’s basically it though, so let’s get to it.

Package quality.

This is a retail package so it has a hang tag and the presentation is conducive to retail displays. The familiar blue and white colors, feature blurbs, and specs are accounted for here, and it’s basically identical to the first edition. Inside, the light rides in a molded plastic carrier with all the accessories efficiently arranged underneath. Here’s what you get:

  • Cyansky K3
  • 2 spare o-rings
  • Spare switch boot
  • Lanyard
  • USB A to C charging cable
  • Cyansky BL2150U 21700 battery (loaded in the light)
  • User manual
  • Warranty card
  • Holster

This is a proper assortment of accessories, including everything needed to get going. The battery has integrated charging which is important because most buyers of this light probably don’t have standalone chargers or 21700 batteries. It featured a plastic isolator to break the electrical connection and was sitting at 3.7 volts. I’m glad to see Cyansky included a nicer lanyard this time and a proper holster. Thanks Cyansky.

Flashlight in use

There’s visually no difference between the version and version 2, so some of this is a bit redundant if you’ve read the original K3 review. As a light meant for professional use, the K3 adopts some design elements from Fenix, and that’s just fine with me. Imitation is a high form of flattery, right? It’s almost like the Acebeam L17 and Fenix PD35 got into a transporter accident, were melded together and the K3 materialized. This is a 21700 form factor light so naturally, the handling is very natural and fits most hand sizes, including my large hands. I’d say it handles a lot like a Convoy M21A with a side switch and pocket clip. 

The finish and interesting gripping texture on the battery tube make for excellent controllability in all grip positions; underhand, overhand, and tactical. Even though there’s no tactical ring with this, I could still hold it fine in a cigar grip. For the switching, there’s a rear mounted forward clicky switch combined with a side e-switch (just like Fenix). The rear switch is for power and momentary use while the side switch is just for mode changes. The click action on both is very good, with great tactile and audible feedback. The e-switch has been upgraded from the first K3 with a central LED indicator for on state and battery state. It’s still silver and has circular ridges for more grip, something missing from the original. Tailstanding is no problem either.

The removable pocket clip allows bezel up or down carry, and it was clipped on pretty tight, requiring a good deal of effort to remove. It has good tension and should do a nice job of securing the light. For the holster, gone is the prior K3’s quasi-half-holster silliness, since they’ve now included a proper holster that fully encloses the flashlight and has a flap for retention. 

In keeping with the tactical theme, you can outfit the K3 with a variety of equally tactical accessories for mounting to a rifle or shotgun  including the RS02 remote switch, GM02 quick detach Picatinny rail mount, GM03 combo mount (with threaded mount), GM06 combo mount and GM09 M1913 Picatinny mount. Interestingly, Cyansky doesn’t sell diffusers or traffic wands for the K3, which is pretty much mandatory these days. Cyansky, if you’re reading this, please offer those.

Build Quality, and Warranty

I was impressed with the first K3’s quality, fit, and finish, on par with anything from Acebeam and Fenix. There were no defects in the machining, no burrs or tool marks, and all the parts fit together precisely with no gaps. All the edges are beveled with no sharp edges. The K3 definitely feels like a quality item and for the level of fit and finish are commensurate with the asking price of around $90 US. 

The light is constructed from A6061-T6 aluminum alloy with black typeIII HA anodizing, and I must say it’s about as good as it gets. It’s nice and matte, and feels amazing in the hands. Very grippy. It’s not like a brick texture, but somewhere in the middle. It’s perfectly done also: no blemishes or thin areas with excellent coverage. 

The light breaks down into four parts: head, battery tube, pocket clip, and tailcap. The bezel is integrated and seems glued on. The tailcap has a single very long gold-plated and decently thick spring mounted on a PCB held in with a substantial aluminum retaining ring. It’s non magnetic, so probably a copper alloy for low resistance. The driver side now features a spring, and that’s a good thing. The first K3 just had a brass contact, and that’s bad, so I’m glad to see Cyansky made that change. The K3 won’t roll away if left on an inclined surface since there are anti-roll cuts in the head, and it passes the Maracas test with flying colors: no rattles.

The front and rear threads are rectangular, thick, and very precisely cut. They are also fully anodized and this makes locking out the light possible by unscrewing the tailcap ever so slightly. Cyansky worked some Jedi magic on the current path because there’s no inner sleeve like Acebeam uses on the clicky/e-switch lights, which is nice because it’s one less item to potentially fail. The threads were a bit dry, but still smooth enough. The battery tube is sealed by a single o-ring, and Cyansky gives the light a generic IPX8 rating, so it should be good for temporary immersion up to 2 meters. 

Although relatively new to the market, Cyansky backs up their quality with a great warranty that rivals the competition: 15 days no hassle free return and refund for defects, 5 year (60 months) free repairs for factory or manufacturing defects, and a limited lifetime warranty with covered labor for repairs (customer covers parts) after 5 years.

LED, Lens, Bezel, Beam, and Reflector

The LED is carried over from the first edition, and it needs no introduction, well, maybe a little. It’s the Luminus SFT-40-W, a 3 volt domeless emitter on the 5050-size footprint. Cyansky doesn’t give the CCT, but everyone and their uncle knows the SFT-40-W predominantly comes in 6000-6500K. With the light 2 meters from the sensor on Turbo, the Opple Lightmaster Pro has the tint coming in at 6493K and 67.3 CRI Ra. The duv is 0.0052.

The LED is perfectly centered in flawless smooth aluminum reflector topped with a toughened mineral glass lens with AR coating. The LED is centered with a round insulating gasket and is perfectly centered. The bezel is unchanged and carries forward the tacticool blacked-out theme. It looks similar to the Fenix TK16 V2.0 bezel as it’s aggressively crenulated and has 3 embedded zirconium breaking tips. Zirconium is one of the hardest natural and man-made materials besides diamond, and comes in between 9 and 9.5 on the Mohs hardness scale.These are for breaking vehicle windows or force-multiplication in defensive situations. I don’t have a spare window to break, so I can’t test this, but I’m sure it would break windows with aplomb.

The beam has a large, but focused hotspot and abundant spill. It’s a very versatile and useful beam, not an all out thrower for sure, but it definitely throws farther than all of my SST40 and SST-SFT70 tactical lights (except the Acebeam L-series). The reflector is tuned very well for the SFT-40 LED. There’s no visible tint shift or corona, and although the beam is free of artifacts, the aggressive bezel does show up in the spill perimeter.

Dimensions and size comparison


Length154 mm6 in
Head diameter40 mm1.6 in
Body diameter25 mm0.9 in

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


Without battery:134 g4.7 oz
With battery206 g7.3 oz

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

Flashlight size comparison with its competition

Group 1 left to right: Cyansky K3 v2, Cyansky K3, Fenix TK20R V2, Fenix TK16 v2, Fenix PD36 Tac

Group 2 left to right: Cyansky K3 V2, Klarus XT11GT V2 Pro, Thorfire C8, Speras E3R

Group 3 top to bottom: Cyansky K3 V2, Olight Warrior 3S Special Edition Ti

Group 4: Cyansky K3 vs Cyansky K3 v2.

Driver & User Interface:

The driver is carried over from the K3 V1. Since the light can take two CR123A batteries, it’s sporting a buck driver. With a buck driver, the input voltage is higher than the LEDs forward voltage, so it must be ‘buked’ or reduced. Since Cyansky bumped the output a bit, it’s probably sporting a new buck controller and inductor with some electrical wizardry.

The UI is pretty straightforward with 5 total modes. The V2 adds a new Eco mode for very low output. Oddly, Eco mode isn’t part of the mode set, but requires both switches to activate.

Modes: Eco, Low, Medium, High and Turbo
Blinkies: Strobe

From OFF:

  • Click and hold side switch: N/A
  • Single click rear switch: Turns on in last mode
  • Half press rear switch: Momentary on

From ON:

  • Single click rear switch: Turns off 
  • Single click side switch: Switches modes (L-M-H-T)
  • Press and hold side switch for about 1 second: Strobe

Mode memory:

  •  Yes, last mode memory

Low voltage warning:

  • The side switch indicator LED shows battery state. Solid green: 100% to 76%, blinking green 75% to 51%, solid red 50% to 26%, blinking red 25% to 0%. When the battery reaches 3 volts, the brightness steps to low, and the light will blink 3 times every 3 minutes and the indicator LED will blink rapidly. 


  • Single variable strobe

Lock-out mode: 

  • None. Unscrew the tailcap ⅛ turn to lock out.


  • To Eco mode: From on or off, press and hold side switch and fully click the rear switch or half press for momentary
  • To Strobe: From ON, press and hold the side switch for about 1 second to activate Strobe. 


  • None

Additional info: Okay, to recap, tactical use or duty light UIs should be easy to use and intuitive to operate (especially under stress), with a Turbo/maximum and Strobe function instantly accessible with a single button click. Sadly, the K3 V2 still doesn’t have those, so it pretty much disqualifies it for serious tactical or duty use. You could argue that if you want instant Turbo, you can switch to Turbo and turn it off so next time you hit the rear switch, voila, instant Turbo, but it’s not the same thing. Additionally, while 5 modes add versatility to a general-purpose light, it is a bit busy for tactical or duty use. Otherwise, this is a nice UI with good mode spacing and all the nice things like thermal regulation (after a 90 second Turbo step down) and visual LVP.

Batteries & Charging

The K3 V2 is basically unchanged from the V1. It’s designed around a 21700, and retains the ability to accept two CR123A primary lithium cells with an optional adapter. Being able to use CR123A cells is a nod towards agencies who do not want to mess with rechargeable batteries and guarantees compatibility with existing lights that use them. Cyansky bundles the K3 V2 with their Cyansky BL2150U battery, which is a button top 5000 mAh 21700 cell with built-in USB type C charging. There’s a tiny hole in the button top for the charge indicator LED: Red for charging, green for charged. 

This battery looks remarkably similar to the 5000 mAh 21700 Fenix includes with their lights, so maybe it’s the same cell with a different wrapper. The good news is this isn’t a proprietary battery, so you aren’t limited to a single battery from the manufacturer. You can use button tops or flat top protected and unprotected batteries in the K3 V2 and while this isn’t a huge deal for the average user who could care less, for enthusiasts who like to swap cells with ones they have on hand, this is a big deal, so major kudos to Cyansky for that.

Since the battery has built-in charging, you don’t need a separate charger, but you could charge this battery in an appropriate charger that takes 75 mm long cells like the VapCell S4+. The charging current on the cell was around 1.6 amps per my Ruideng AT35 USB meter. Not that great considering this is a 5 Ah cell. It took a few hours to fully charge, so don’t expect quick recharges.

Performance test

Lumen measurements

Lumens are measured in my 50 cm integrating sphere with a Digi-Sense 20250-00 data logging luxmeter. The sphere has been calibrated with a Convoy S2+ measured to 260 Lumens and the figures are within 10% of actual. I used the included 5000 mAh 21700 which was fully charged for the readings. Amps are measured with my Thisinde B18 Plus multimeter with 14 gauge wires on banana plugs and higher currents with my FY219 clamp meter with a loop of 12 gauge wire.

ModeAmps at startSpecifiedturn on30 sec10 minutes
Eco22.4 lm2.4 lm
Low70 mA3030 lm30 lm
Medium316 mA150165 lm165 lm165 lm
High946 mA450418 lm418 lm418 lm
Turbo6.3 A20001771 lm1611 lm677 lm

Parasitic drain:

  • 3.5 µA

Cyansky increased the V2’s output a bit to 2000 Turbo Lumens vs 1600 for the V1. That doesn’t seem like much of a bump, and the results show it really isn’t. The first K3 managed about 1500 Lumens on Turbo, so we’re not seeing much of a bump. In comparison, the Fenix TK20R V2 is doing almost 3000 Lumens in its Turbo mode. 

Battery Life: Runtime graphs

Runtimes are measured in my 50 cm integrating sphere with a Digi-Sense 20250-00 data logging luxmeter. The sphere has been calibrated with a Convoy S2+ measured to 260 Lumens and the figures are within 10% of actual. I used the included 5000 mAh 21700 which was fully charged for the tests.

ModeSpecifiedMeasured runtime (ANSI)Time till shut off
Eco200 h
Low66 h
Med16 h13h 59min13h 59min
High4 h 30 min4h 37min9h 11min
Turbo*2 h2h 14min4h 12min

The runtimes look really good, and about what I expected, except for Medium, which is about 2 hours short. The shutdowns are preceded by LVP blinks starting about 15 minutes from the shut down and a flashing switch LED, so you get plenty of warning to switch or charge the battery. The light was not usable after each test, and the battery read a bit low at 2.57 volts after the test. The output is very steady and constant, which is awesome and very important for a professional-use light. Heat was also never an issue, and the light was hand-friendly the entire Turbo and High runtimes. 

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.

Peak beam intensity and beam distance measurements

Beam distances are measured using a Uni-T UT383S luxmeter measured indoors at 5 meters with the fully charged included battery. Measurements taken at 30 seconds.

ModeSpecifiedCandela measured MetersYards
Eco0.25 cdN/A
Low441 cd725 cd5459
Medium9820 cd9975 cd200218
High28,561 cd27,725 cd333364
Turbo124,690 cd103,875 cd645705

Cyansky specs the throw for the V2 at 700 meters (vs 600 for the V1) so there’s a bit of an improvement in beam distance. Eco was too low to measure at 5 meters. The throw is very impressive for a 40 mm head, and more than enough reach for most tasks you’ll grab the K3 V2 for. The similar offerings from Fenix and Nitecore and Acebeam (except the Acebeam L1x series) don’t have throw figures like this.

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). Columns Meters and Yards show rounded numbers.


I compared the K3 V2 to some other tactical use and duty flashlights. Photos were taken with my Samsung Note 8. The 40-meter shots with the camera set to 0.3s ISO 200 and 5000K WB.

Beamshots of the following flashlights compared:

  • Cyansky K3 v1
  • Cyansky K3 v2
  • Fenix PD36 Tac
  • Fenix TK16 v2
  • Fenix TK20R v2
  • Klarus XT11GT Pro V2
  • Streamlight Stinger 2020
  • Olight Warrior 3S Special Edition Ti
  • Thrunite BSS V4

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

Final Verdict


  1. High quality with solid construction
  2. Fully regulated runtimes and output
  3. Non-proprietary battery
  4. Simple UI
  5. Great beam with lots of reach
  6. Ceramic glass breakers


  1. Still not a tactical/duty-ready light
  2. Output is down from spec
  3. Could use more output

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

Reviewer Nick
Author: Nick

4.5 stars: ★★★★⋆

Although they’ve not arisen to the same position of Acebeam, Fenix, or Nitecore, Cyansky has cranked out some very nice flashlights, which says a lot since they’ve only really been a presence in this market for a year or so. When it was introduced last year, the K3 represented a nice entry into a pretty crowded and competitive market segment, competing against offerings from Fenix and Nitecore, but still coming up a bit short in the output department and tactical and duty-use feature sets (missing direct Turbo/Strobe, and lame output).

I was glad to see a V2 rolled out, but has the upgraded version brought any improvements to the existing light? I did see a slight bump in output from the first version, but it’s still a bit down from the competition (which are sporting 2500 and 3000 Lumens). I do like the LED indicator on the side switch, and the added Eco mode is nice, but otherwise it’s more of the same. I was hoping for a revised UI with direct access to Turbo and Strobe from off, but no dice this time, so it’s still more of a general purpose light rather than a duty or tactical use light. In that role, I really like the K3 V2.

The UI is simple, and the beam is very nice with lots of reach for its size. The output is fully regulated as well. Battery compatibility is also good, and the usual niceties I’ve come to expect from Cyansky products are present and accounted for: Solid build quality, nice finish, great attention to detail, and a great warranty. While not the upgrades I was hoping for, I’m giving the K3 V2 4.5 stars.

Cyansky K3 v2 for sale

1lumen selects and reviews products personally. We may earn affiliate commissions through our links, which help support our testing.