Cyansky K3 Tactical Flashlight Review

The Cyansky K3 Tactical is a new flashlight by Cyansky offering a dual switch interface, the new Luminus SFT-40-W emitter, and a tactical feature set.  Read on for testing!

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Official Specs and Features of the Cyansky K3 Tactical Flashlight

Here’s a link to the Cyansky K3 Tactical flashlight product page.

Versions

There is only one version of the Cyansky K3 Tactical flashlight.

Cyansky K3 Tactical Flashlight Price

With cell (as seen in this review) the Cyansky K3 Tactical flashlight costs $84.95.

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Short Review

Cyansky fills an interesting market.  They make quality products and seem to be a great up-and-coming brand.  This Cyansky K3 Tactical flashlight is no exception.  This is the first SFT-40-W flashlight I’ve seen, and the performance is quite good.  The Cyansky K3 Tactical offers great build quality, and looks nice too!

Long Review

The Big Table

Cyansky K3
Emitter:	Luminus SFT-40-W
Price in USD at publication time:	$84.95
Cell:	1×21700
Turbo Runtime Graph	High Runtime Graph
LVP?	Not really
Switch Type:	Both
Quiescent Current (mA):	–
On-Board Charging?	Yes
Charge Port Type:	USB-C (On cell)
Charge Graph
Power off Charge Port	–
Claimed Lumens (lm)	1600
Measured Lumens (at 30s)	1451 (90.7% of claim)^
Candela per Lumen	65.8
Claimed Throw (m)	600
Candela (Calculated) in cd (at 30s)	2820lux @ 5.95m = 99835cd
Throw (Calculated) (m)	631.9 (105.3% of claim)^
All my Cyansky reviews!

^ Measurement disclaimer:  Testing flashlights is my hobby. I use hobbyist-level equipment for testing, including some I made myself. Try not to get buried in the details of manufacturer specifications versus measurements recorded here; A certain amount of difference (say, 10 or 15%) is perfectly reasonable.

What’s Included

• Cyansky K3 Tactical Flashlight
• Cyansky 5000mAh 21700
• Charge cable (USB to USB-C)
• Spare o-rings (2)
• Spare switch cover
• Lanyard
• Nylon pouch/sleeve
• Manual

Package and Manual

This nice little note is included on a hang-tag on the light.

 

Build Quality and Disassembly

As I said above, the Cyansky K3 Tactical flashlight is a very well-built light.  Cyansky does this… they build very nice lights!  I’ve reviewed a bunch of them, and even in categories I might not chase, it’s easy to note that the lights are still nice quality.

This is a “tactical” flashlight – though I’m not certain what the qualifiers are for “tactical.”  Strike bezel?  Check.  Dual switch interface?  Check.  Momentary turbo or strobe?  Hold up wait…

Here’s the top-down view.

The head – the biggest diameter part, that is – looks to be removable.  I was unable to unscrew that part, though.

Cyansky touts this bezel as a zirconium bezel.  I don’t doubt that but I do think it’s those little inset balls (the glass breakers) that are zirconium and not the whole crenelated part you can see below.  (In fact I don’t even think that’s a separate part from the head itself).

Below you can see the tailcap removed.  The spring is just a little proud (and that’s fine).  The threads are square-cut, anodized, and lightly lubed.

Inside the tailcap you can see that the spring is quite long.  The head doesn’t have a spring at all, which doesn’t support the idea that this is a tactical flashlight.  You can correct me if I’m wrong about that!  The idea is that dual springs would keep cell contact during weapon recoil.

On the other hand, this tailcap spring is very beefy and might stand up to recoil fine.  I turned on the light and banged it around a bunch and the light stayed on.  But I didn’t test it with recoil.

Size and Comps

Head diameter: 40mm
Body diameter: 25.4mm
Length: 151mm
Weight: 133g (without cell)

If the flashlight will headstand, I’ll show it here (usually the third photo).  If the flashlight will tailstand, I’ll show that here, too (usually the fourth photo).

Here’s the test light with the venerable Convoy S2+.  Mine’s a custom “baked” edition Nichia 219b triple.  A very nice 18650 light.

And here’s the light beside my custom-engraved TorchLAB BOSS 35, an 18350 light.  I reviewed the aluminum version of that light in both 35 and 70 formats.

You had to know I’d do this….

Retention and Carry

You’ll probably notice the pocket clip first, though there are a few options for carry.  The clip is a standard friction fit variety.

This clip fits only on the tail end of the Cyansky K3 Tactical flashlight.

Next for carry is the lanyard.  You could likely attach the lanyard on the pocket clip, but I’d go with these two holes on the tail end instead.

Only one side of the tailcap has this hole set.

The lanyard is what I’d probably describe as “nothing special.”  It gets the job done, and is quite lanyard’y, but overall is just a simple piece of cord with an adjuster.

Finally, there’s this nylon sleeve.  It’s not really a pouch (as I’d say “pouch” implies “closed”).  It’s very suitable for belt attachment and allows easy access when mounted this way.

Power and Runtime

The Cyansky K3 Tactical flashlight is powered by a single lithium-ion cell.  Cyansky includes an appropriate cell – a 5000mAh 21700, the BL2150U.

As far as usage goes, this is a standard button top 21700.  It has some additional features, which I’ll cover below.  This is the same cell that’s used in the other Cyansky 21700 cell lights.  My flat top 21700’s don’t work in the K3!

That said, a button top 18650 will work in a pinch, but it’s loose inside there.  It’s the button that’s important here.  Button top cells will work.  Flat-top cells will not work.

The cell fits into the K3 in the usual way – positive terminal toward the head.

Here are a couple of runtimes.  There’s a big stepdown at around 1.5 minutes, but then the light holds around 900 lumens for over an hour.

Output on high is flat for over two hours, at around 750 lumens.

In the runtime graphs above, and on bench power, I did not observe low voltage protection.  This is sort of to be expected with a tactical flashlight.  The light steps down to “very low output” at around 2.6V and then finally shuts off (ish) at 2.5V.

Charging

As stated, the cell has some other features too.  There’s built-in USB-C charging, by way of a USB-C port on the positive terminal end.

Another feature is a little indicating LED right in the positive terminal of the 21700.  When charging, this indicator is red.  When charging is complete, the indicator is green.  Otherwise, the indicator is not on at all.

An appropriate cable is included – USB to USB-C.

Charging proceeds at a fairly slow 1.5A or so, which is well under 0.5C for this 5000mAh cell.  Time required is around 3 hours, and the terminal voltage seems to be consistently 4.19V, a very good termination voltage.

Modes and Currents

Mode	Mode Claimed Output (lm)	Claimed Runtime	Measured Lumens	Tailcap Amps
Turbo	1600	2h	1451	4.66
High	800	3h	747	1.67
Med	200	12h		0.33
Low	30	100h		0.03

Pulse Width Modulation

No real PWM on any mode.  Low shows some squiggles, which I don’t believe is PWM.

Here you can see a “baseline” – a chart with almost no light hitting the sensor.

Then there’s the Ultrafire WF-602C flashlight, which has some of the worst PWM I’ve seen. It’s so bad that I used a post about it to explain PWM! Here are multiple timescales (10ms, 5ms, 2ms, 1ms, 0.5ms, 0.2ms) to make comparing this “worst” PWM light to the test light easier. That post also explains why I didn’t test the WF-602C at the usual 50us scale.

User Interface and Operation

Two switches are used for control of the Cyansky K3 Tactical flashlight.  First is the mechanical tail clicky.  It’s a forward clicky, which allows momentary actuation.  This switch also serves as a mechanical lockout to prevent any parasitic drain on the cell

The switch cover is big but the switch itself is normal-sized.  It’s not terribly thick, so you can feel the actual switch underneath.  The clicky is very clicky and the action is low.

The second option for operation is the e-switch on the side near the head. This switch is metal(ish?) and very proud.  Also, it doesn’t compete with anything else, so it’s very easy to find without looking.  Notably this switch (cover) is improved from lights like the H3, which is otherwise a very similar flashlight.

The user interface is not complicated.

Here’s a user interface table!

State	Action	Result
Off	Click Tail Switch (TS)	On (last used mode, except strobe)
On	Click TS	Off
Off	Click Side Switch (SS)	No action
On	Click SS	Mode advance L>M>H>T
On	Hold SS	Strobe
Strobe	Click SS	Return to the previous mode

For this being billed as a tactical flashlight (and also “looking like one”), it’s surprising that there’s no easy or direct access to turbo or strobe.

LED and Beam

The emitter is a Luminus SFT-40-W. A smooth deep reflector is used here.

The bezel is crenelated, so light will shine out when headstanding (and on).

Again, Cyansky bills this bezel as zirconium, but I suspect it’s just those three-strike points that are zirconium.  They aren’t sharp; these are tiny spheres.

These beamshots always have the following settings:  f8, ISO100, 0.3s shutter, and manual 5000K exposure. These photos are taken at floor level, and the beam hits the ceiling around 9 feet away.

Tint vs BLF-348 (KillzoneFlashlights.com 219b version) (affiliate link)

I keep the test flashlight on the left and the BLF-348 reference flashlight on the right.

I compare everything to the KillzoneFlashlights.com 219b BLF-348 because it’s inexpensive and has the best tint!

Conclusion

What I like

• Great output
• Great throw
• Simple user interface
• Brand user interface consistency
• Excellent build quality
• Cell is included
• No PWM

What I don’t like

• Cool white
• No direct access to strobe or turbo
• Cost is a little high for a new-ish brand

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Notes

• This light was provided by Cyansky for review. I was not paid to write this review.
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