The head of the TK20 is made up of 2 parts which are adhered together providing a waterproof seal for all the components. Up the front the TK20 has a smooth bezel with an AR coated glass lens sitting slightly recessed below the bezel. I personally would have preferred the lens to be slightly deeper in to reduce the chances of damage, since the TK series are meant to be used under tough conditions. Sitting behind the glass lens is a smooth aluminum reflector which has been nicely polished and finished overall. While there are very fine radial rings due to the machining process running down the reflector cup, they shouldn't have any significant affect on the beam profile. The LED sitting at the bottom of the reflector cup is well-aligned, perhaps just a hair off perfect center. On it's exterior, the head has wide band of striped knurling which provides adequate grip for twisting the head. The rear half of the head is slightly raised and has scallops machined on which seem to be a design element. Initially I though these would serve as an anti-toll feature, but they do know do so, at least not very effectively anyway. As can be seen from the rear view of the head, the "+" battery contact incorporates a physical reverse polarity protection by means of the two slightly raised crescent-shaped metal contacts. Threads are very well machined, clean, smooth and not too fine.

The first thing that I immediately noticed about the battery tube is the thickness of its wall. The TK20 may well have the toughest battery tube of any flashlight I've seen, with a wall about 3mm thick. For grip, Fenix decided to go with a rubber sleeve with a wave texture over the battery tube instead of traditional knurling. This rubber sleeve provides improved friction over a knurled metal surface especially when the light is wet, or if you have sweaty palms. However, one thing I didn't like about this rubber sleeve is that it isn't fitted tightly around the battery tube and is able to twisted around rather easily. Threads on either ends are well machined with a rubber o-ring placed on either ends as a seal against moisture. The threads on the rear are anodized so the light can be locked-out by loosening the tail cap to prevent accidental activation. There's a slightly raised lip at the front end of the battery tube with two screw holes, this is where you may attach the included clip with hex screws. The screw holes don't go all the way through the wall of the battery tube so there's no worry of water seeping in even if you don't attach the clip. The tail cap has a simple and functional design, its rear end is scalloped to that it would be easy to engage the switch while still allowing the light to tail stand quite stably. There are 2 wide slots for lanyard attachments as well. The TK20 uses a forward push button so momentary activation is possible. It has an average amount of tension and travel, and also provides a positive tactile feedback when clicked.

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

The TK20 is advertised to output 150 lumens on Turbo, and 45 lumens on General mode. The lumen ratings on the TK20 is generally lower than other current Fenix models is because it uses a lower Q2 binned XR-E LED with a warmer tint, instead of a Q5 or higher bin which usually have cool tints. This supposedly helps to provide improved color rendition as compared to the generally cool color temperature of XR-E LED's. It works better at illuminating object in foggy conditions.

The beam profile produced by the TK20 has a tight spot meant for illuminating objects at distance, not very useful for close up work since the spot is so focused. There are some ring-shaped artifacts due to the use of the smooth and slightly misaligned reflector. However in practical use, these minor issues will not impair in any way. The output intensity is intense in the hot spot with usable spill for peripheral vision. Runtime is well maintained as with most Fenix products and regulation is also very good for most of the battery life before dropping sharply at the end.

The Good - Very tough, solid build quality and cleanly machined. Overall good fit and finish. Tactile and responsive switch. Good runtime and regulation.

The Bad - Rubber grip can sometimes slip around the battery tube.

The Relative - Warm beam color tint. Heavier than most other 2x AA lights due to rugged construction. Some minor beam artifacts. 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).