The entire head of the TK10 is machine from aluminum with a 3-point crenellated bezel which allows you to see if the light has been left on when placed head down. Beneath the bezel sits a toughened, AR coated glass lens similar to other Fenix products. A smooth reflector is used in the TK11 which provides a sharply focused beam with some artifacts. The emitter and reflector are perfectly aligned in my sample. The exterior of the head has 6 shallow scallops machined on it which serves well as an anti-roll feature. The hard anodizing on the head is pretty well done with consistent coloring. This is probably due to the thickness of the coating. Its purely cosmetic though, the surface still feels smooth. Looking inside the rear end of the head you'll see the PCB for the "+" battery contact though do take note that the TK11 does not have the reverse polarity protection implemented so that it will work with flat-topped 18650 cells. The threads on the head are smooth, clean and thicker than previous Fenix models.

The battery tube maintains a fairly clean look, the TK11 has cooling fins machined at the front of the battery tube instead of the thick raised neck of the TK10. There's a band of diamond textured knurling about 3cm wide, and two flat surfaces machined on with the Fenix branding printed on it. The TK11 has great ergonomics, it feels really comfortable and secure in hand with a hefty mass. I did find the grip ring to be slightly uncomfortable when holding the TK11 in an overhand grip, and it's also a little small for comfortably holding in a cigar-style grip. The wall of the battery tube is very thick, I'm confident that it can handle rugged abuse. Its internal diameter is wide enough to accommodate protected 18650 cells easily. Threads on either ends of the battery tube are very well done, smooth and thick. Head and tail cap screw on very easily without any cross-threading or grinding, very nice. There are thick rubber o-rings which came generously lubricated. These serve are water seals, 2 at the front end and 1 at the rear end. The TK11 is advertised as meeting IPX-8 waterproof standards, although maximum submersion depth wasn't specified by the manufacturer. The threads at the rear end is coated as well so the light can be locked-out by loosening the tail cap. Type 3 anodized coating on its exterior surface is smooth and consistent throughout.

The tail cap has a hand of knurling for grip. At the rear end the tail cap has a deep 4-point scallop machined into it, one of the points has a hole for lanyard or key ring attachments. This design allows for easy switch activation while still allowing the light to tail stand on flat surfaces. The rubber switch cap has a checkered texture and feels quite thick. The switch module housed in the tail cap is a forward push button, allowing for momentary activation which I personally think is a must-have for tactical flashlights. The switch has a noticeably longer travel than other Fenix products which use reverse push buttons. Clicking on the switch provides good tactile feedback and audible click. Switching mechanism is responsive so signaling with the TK11 poses no problems.

If you're unfamiliar with any of the terms used in this review, click here for explanations on common flashlight related vocabulary.

The TK11 produces a very tightly focused hotspot due to the use of a smooth reflector. It throws significantly further than the TK10 which uses a textured reflector. Due to this, the beam area has some artifacts such as a dark ring right around the hotspot and a feint yellow ring too. Beam tint is a neutral white on General mode and shifts to a slightly cooler tint on Turbo mode.

The notable feature of the TK11 is that it now officially supports the use of a 18650 cell. The circuit used in the TK11 is different that that used in the TK10 as it allows a 3.7V li-ion cell such as a 18650 to power the light up to full brightness instead of about 75% as the TK10 did. Regulation isn't as consistent as the TK10 when using 2x 16340 or CR123 cells, output seems to increase slightly as the cells run down. The TK11 struggles to maintain regulation with 18650 cells on Turbo mode. Runtime is good considering the variety of input voltages the TK11 accepts.

The Good - Solid build quality and cleanly machined. Nicely designed anti-roll surfaces and grip ring which work well. Tactile and responsive switch.

The Bad - Grip ring is uncomfortable when held in an overhand grip and is slightly too small to hold securely in a cigar-style grip.

The Relative - Neutral white beam tint. Uses a forward push button which allows for momentary activation.

Head (front view).

Head (side view).

Head (rear view).

Battery tube (front view).

Battery tube (side view).

Battery tube (rear view).

Tail cap (front view).

Tail cap (side view).

Tail cap (rear view).