Review: Xtar Wk21 with measurements and outdoor beamshots

Xtar Wk21

Xtar has made flashlights, batteries and chargers for some time. In this review I am looking at a small high power light, that uses a LiIon battery to drive a XM-L led.
The light is turned on/off and brightness changed by loosing and tighten the head. The light is made of aluminum with anodized finish.

The light comes in a a small box with a foam insert.

Included in the package is the light, a LiIon battery, a chain with claw and split ring, a manual and a warranty card.

The light uses a smooth reflector with a XM-L led. With this small reflector and a XM-L led the beam will be mostly flood.

The head has some groves for grip, but is not equipped with any cooling fins.

The light has up to five modes, that can be selected with loosing/tightening the head. It will remember the last selected mode.

A look at the head from the backside shows that there is a metal plate on the plus connection, but also show 4 small solder pads. Bridging any of these pads will disable one mode from the user interface, the only mode that cannot be disabled is high. How to do this is well explained in the manual. On the last picture I have disabled SOS mode and there is also some solder on strobe, but it is not bridged.

The battery tube has triangular threads with anodized.

Inside the battery tube is the usual spring.

On the tube is a removable clip.

The tailcap has a magnet below the round plate. The magnet is strong enough to attach the light to a fridge. The plate can be unscrewed and the magnet removed, for people that do not want a magnet.

Here is all the part the light can be disassembled in without tools.

The light is small and bright and has a lot of flexibility both for modes and for physical configuration with/without magnet and clip, but it is not designed for long runtime. I like this light, it is a nice EDC.

Technical specification and measurements

The light is rated for use with one 16340 LiIon battery.

Measured size and weight:
Length: 71 mm
Diameter: 22.4 mm to 25.6 mm
Weight: 70 gram with Xtar 16340

The light uses a Cree XM-L T6 led.

In the above table I have collected all modes. The current is measured at 3.7 volt. All the estimated runtimes are with a 600mAh LiIon battery. The estimated lumen is scale from the specified maximum of 500 lumens.

The first voltage sweep is done in high mode. The light uses a linear current regulator, i.e. the current draw does not change with voltage.
Also note that the current draw has fallen to around 0 at 2.6 volt, this does give some protection for LiIon batteries.

Reducing the brightness to medium with 40% pwm reduces the power consumption to about 40% of high.

At low there is not much regulation, it is just low brightness.

The light does not last long at high, it is better at medium, but this is definitly not the light to use for long runtime and lot of light at the same time (Larger batteries are needed for that).

The strobe is 10 Hz and has a 50% duty cycle. It runs at full brightness.

SOS is not really a SOS, it only sends SO, the last S is missing.

The light uses pwm at 500 Hz to control brightness, here is medium.

Pwm at low.

Comparison to other Flashlights

Xtar Wk21, Xtar Wk25B, Xtar Wk26:

Sunwayman V10R Ti, Fenix LD15, Fenix E15:

For the full comparison to other lights with graphs and beamshots see here


The light was supplied by Xtar for review.

Keep up the good work .

i am not interested in XTAR torches (i dunno why lol) (maybe because i am broke) and i saw your series of new reviews on cpf but since i am permabanned there, please have my thanks here.

Great work, yes please keep it up!

You're not into reviewing budget torches are you? ( Romisen, Lumintop, Tank007 )

I am most to the more expensive models, but I have included some budget lights in my AAA comparisons.

Thanks again HKJ! Frontpage'd and Sticky'd.

HKJ what's your honest opinion on this flashlight? How long did it stay with all 5 mode enabled?

As I wrote: I like it. I have something for small very bright lights, even if they have short runtime on max.

The SOS got killed rather fast, a strobe is enough flashing for me.

I have mine set to just low-mid-high. I disabled the flashy modes.
It’s a fun light, when people see it on high they can’t believe how such a small light can be so bright

From this review I bought 2 some time ago. 1 of the best flashlights I have. Super bright, built like a tank, very EDC-able. Just love them. Would be about the last light I’d part with. What I love about these forums are excellent reviews like this that put you onto great lights like these.

Had mine about 4 months and this is my go to light for everything around the house, thinking of only having the low-mid-high mode and was wondering how easy it was to do it?

I now have two of these amazing little lights, I got a three mode one from ebay and much prefer not having the flashy modes,

I am now waiting for the UniqueFire UF-K21 from dx

to see how they compare :)

I have one in a drawer somewhere. I don’t really care for it. There’s nothing wrong with the light itself, I just think its ugly. It reminds me of something that would have been produced in the Soviet Union in the seventies.

did you mean the xtar.

Ya, the WK21. Like I said, there’s nothing wrong with it, I just personally don’t like the look of it.

When I reviewed this great little light a while back (a year?) somebody responded saying you could simply slide a pencil tip back and forth over the contacts, effectively filling the line between with lead. Xtar sent me 2 lights with this feature and the pencil trick worked perfectly on both lights, with the added benefit of being able to reverse the process.

If I remember correctly, I filled in all 4 contacts so it would be single mode/high.

Anyway, great job HK.



If you find it in your drawers, I’ll be glad to take it :)!