Fenix has almost created the perfect weaponlight with the TK16 imo.  



First the end cap.  Best design ever imo.  An on/off button (the round button).  Press it a little and it's momentary on/off.  Press it hard and more and it clicks on/off.  

The other button is angled and cycles thru the power levels and if pressed for more than a second engages the momentary 1000 Lumen strobe on/off as long as it is held down.   The strobe switches between a very fast strobe and a fast strobe (still multi-flash per second) about every 4 seconds and is very disorienting.

The light remembers what power setting you have it on.  No need to cycle thru the power settings each time to get it where you want it.

You also don't have to worry about accidentally bumping the angled button and changing the power setting when the lights not on.  It only changes the power setting when you have the on/off button on at the same time.



Could you accidentally press the wrong switch?  Not really.  They are not really in the same place and don't feel the same at all.   I am running mine with a Vltor QD Mount at 11:00 and it's perfect.



Here's a stock pic of the light.  The head of the Fenix TK series lights is thick aluminum.  I think you could easily knock someone out with this light with an 18650 battery in it.    

It has a snap-on stainless clip that you'll be removing when using as a weaponlight and a screw on aluminum anti-roll nut.   Anyway, if you remove the end cap, then you can remove this nut, and you'll want to because it will prevent you from sliding the light into the rings of many mounts including a Vltor QD Mount.

And here was the first issue I had with this light.  I tried to remove the anti-roll nut and it was binding on the o-ring that butts up against a little flange that the end cap snugs down on.
Hmmm... the same nut on my old Fenix TK11 unscrews without binding on the O-ring with no problem.   I ended up having to remove the o-ring to get the anti-roll nut off then put the o-ring back on.
No biggy but this does leave a small section of threads visible where the anti-roll nut is missing but they are anodized black so it doesn't look bad.  

So I removed the anti-roll nut, screwed the endcap back on and then tried to slide the light into the Vltor QD mount and I found the one thing that was a little aggravating.  The end cap is just a little larger in diameter than the tube, maybe 1/32 larger?.  It's just enough to prevent the light from sliding into Vltor QD mount rings without first removing the end cap.   On my old TK11 the end cap is the same diameter as the tube and this is not a problem.  Maybe they made it a little larger on the TK16 because of the two buttons?   It's a nit.



The Vltor mount really tucks this light into perfect position.  Note the QD lever on the Vltor mount.  See how it locks down to the rear?  It doesn't come this way.  Out the box it locks to the front which
creates a snag hazard imo.  But it's easy to reverse.  Just remove the nut all the way used to adjust the mounts tension, reverse the lever, and put the nut back on.  Be careful not to let the springs fly out.

To sum it up, if Fenix really wanted to make the perfect weaponlight I would say take the TK16, ditch the clip and the anti-roll nut and shave a hair off the end cap so it would be the exact same size as the 1" barrel and they would be it.  But it's close enough as is that I really don't think there's anything else close.

These lights are currently going for about 79.95 on amazon

It's reasonably well built, but....

- Too big, bulky.
- Too heavy.
- I prefer a switch which is dedicated either to momentary-on or constant-on. Fine motor skills disappear in tense situation.

I prefer something like the Inforce WML series.  Yes, they've had some issues but they've addressed them.  The Fenix series also has had issues, like switches failing.

ETA - I own several Fenix's, TK-21 etc, and all have been reliable.  Also the idea of an angled switch on the TK-16 appears to be have been copied from the Inforce WML.

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I read this post below and passed on the Inforce... No way I would remember to do this every time I put my rifle in the safe.

"Just a heads up,
Got my Inforce WML a few weeks ago. Set it up on my rifle with a fresh battery. A week later I took it out of the safe and the light didn't turn on. Switched to a fresh CR123 and it worked again. Activated the safety lever just in case the light activated in my safe and discharged the batteries (which it didn't). A week later I took my rifle out of the safe again and the second battery was again dead. I contacted Inforce and they said if you do not unscrew the headcap 1/4 turn then the light will discharge on its own. Just wanted people to be aware of this as I did not read anything about this before purchasing. Not ideal for a HD/patrol rifle IMO since you have to remember to unscrew the headcap and rescrew it before using the light."

http://www.ar15.com/forums/t_3_20/642966_Inforce_WML_batteries.html

But I agree, the TK16 is a pig.  But it's also 1000 lumens.  I just figure it's kinda like how a 30 round loaded mag weighs more than a 20 round loaded mag.

As I stated before, Inforce had some issues with their first model and has resolved them.  My initial sample did indeed have the battery drain issue.  I contacted them, shipped it back, and they sent me a brand new UPGRADED model, no questions asked.  Can't ask for better service than that.  There is no battery drain problem on a properly functioning WML.  It's not true that you MUST unscrew the light 1/4 turn to avoid drain.  That is just a precaution to use during transport where something may bump up against it and push the button, same as any other light. (Note that the WML also has a little "safety" lever that you can swing up to protect the button.) It surely doesn't hurt to unscrew it during long term storage either. But it's not necessary.

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I still prefer push button momentary / twist constant on for weapon lights.    Been pleased with the Fenix stuff I own, though.