The Olight T20 is a solidly built light, with good ergonomics and a solid structure. As you can see from the image to the right, the head houses a unique reflector cup which is half smooth and half textured. The smooth surface area reflects a highly focused hot spot for optimal throw, while the textured surface area smoothens out any artifacts in the spill region of the beam profile. Its an innovative take on reflector design and produces a beam that is characteristic of Olight products. The emitter is just slightly off-center, but not by much. On the exterior, the head has a thin band of checkered knurling which provides some grip when you're twisting the head. The Type 3 hard anodized coating is smooth and consistent throughout, free of scratches or smudges. The threads on the head are a similar to those on the Fenix lights, not too thin or too thick relative to its overall size. There may be some squeaking initially due to some machining dust stuck between the threads, but a quick clean with a stiff bristled brush will fix this. The threads on the head also sometimes cross-threaded during my tests, however I don't think this would be much of a problem since you wouldn't need to completely remove the head while using the T20. The head's exterior is of a hexagonal shape which serves as an anti-roll feature.

The battery tube has a simple and clean looking design. There's only one flat face machined onto the tube, which is where the Olight branding is printed on. There is a band of knurling about 2cm wide for additional grip. The area towards the end is slightly slimmer, this provides good ergonomics for when you're holding the light in a cigar/pistol grip. The walls of the T20's battery tube is thinner than either the T10 or T15 models. The battery tube is wide enough to accommodate even the thickest 16340 cells without problem. As with the head, coating on the battery tube is just as well done. Very smooth and consistent. The threads between the battery tube and the tail cap are cut very smooth. I noticed that the more force you apply while screwing on the tail cap, the higher the chances of it getting cross-threaded. Otherwise, it screws on perfectly fine and smooth. The tail has a hexagonal design similar to the head and provides good grip when unscrewing the tail cap for battery changes. Housed inside the tail cap is a reverse push button switch module. It seems identical to the ones found in Fenix lights. Everything from its tension and positive tactile feedback, to the clicking sound it makes is identical, which is a good thing. The T20 can tail stand without problems since the rubber button cap is slightly recessed from the end of the tail cap.

The user interface of the Olight T20 is similar to the NiteCore Defender Infinity (ES) which was reviewed earlier in the sense that switching between brightness levels and strobe/S.O.S. modes are done by separate mechanical actions. Brightness is cycled by twisting its head, while strobe/S.O.S. is done by half-pressing the push button. The instructions on the box doesn't say how quick these half-presses should be, but it seems anything between 1 second is sufficient to change the modes. This user interface is a nice alternative is you don't quite like the cycling of levels via push button. One thing I didn't like about the cycling of brightness levels is that it cycles from brightest to dimmest level. Personally I would think it makes more sense to cycle from dimmest to brightest.

The color temperature on my sample is slightly cool. The spot is well-focused and the spill beam is smooth without artifact thanks to its unique reflector design. There is a slight dark area right in the middle of the hotspot, but its not noticeable in practical use. The T20 can run on either CR123 or 16340 cells as advertised by the manufacturer. Unlike the T10 and T15 models, all levels work perfectly when powering the T20 with 2x 3.6V/3.7V li-ion cells.

Here's a rundown of the modes available and how they're accessed.

Constant Illumination:
Click on the push button, cycles through the 5 brightness levels by loosening then tightening the head within 1 second each time. Brightness level is memorized even when powered off.

Strobe:
Half-press the push button while on any level in Constant Illumination mode. Light will strobe on its brightest level. Mode is not memorized, light will revert to constant illumination mode the next time its turned on.

S.O.S. (Low Brightness):
Half-press the push button while in Strobe mode. Light will blink the S.O.S. sequence on low brightness level. Mode is not memorized, light will revert to constant illumination mode the next time its turned on.

S.O.S. (High Brightness):
Loosen then tighten the head within 1 second while in S.O.S. (Low Brightness) mode. S.O.S. sequence will now blink on high brightness level. Mode is not memorized, light will revert to constant illumination mode the next time its turned on.

The Good - Very well built and finished. Provides a well-focused spot while still having a smooth, artifact-free spill beam. Holds excellent regulation well while providing good runtime.

The Bad -Brightness level cycles from brightest to dimmest.

The Relative - Half textured and half smoothened reflector provides a unique beam profile. Beam's color temperature is slightly cool. Uses a reverse push button.

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).

3800 Lux