Body:he battery tube continues the same deign of having ample knurling all over the external surface, albeit with the additional of four flat faces machined along its length. The entire light is made of Ti-6Al-4V titanium alloy. There is a narrow section towards the front which is smooth and polished and has branding and serial number engraved on. A rubber o-ring sits All this knurling is proved to be really practical since the light rather small and its twisting mechanism is rather stiff as well. Using an Eneloop AAA proved to be a tight fit which contributes to the stiff twisting resistance. On the plus side, this also means that it's less likely for the ET10 to be accidentally activated when stored. I found it rather difficult to single-handedly activate the light from the off position, although switching between Low and High was much easier. The rear end has a threaded on tail section which isn't meant to be removed under normal use. It has a hole for lanyard attachments and also a tritium slot. The rear end is flat and allows the ET10 to tail stand without problems. Overall, the ET10 feels somewhat heavy for a titanium light. The ET10 is advertised as being waterproof down to 10m and drop-resistant according to US-MIL-S-TD-810F standard.

Bezel/Head: The ET10 is one of the smaller lights in VersaTi line of titanium products. The head has a smooth bezel up the front which is pocket friendly, without any aggressive crenellations. Behind this sits a sapphire lens which is "waterproof coated" on both sides, although it doesn't seem be AR coated from visual inspection. The ET10 doesn't have a traditional reflector, instead there is a very shallow and narrow polished cup surrounding it. The entire front section of the head which holds the lens and cup can be removed by simply unscrewing it, and exposes the bare LED and the brass heat sinking it sits on. Externally, the head is entirely covered in a diamond textured knurling which is noticeably rougher than most. From the rear end, the "+" battery contact point can be seen, along with the contact mechanisms which control the output activation of the light. Threads between the head and battery tube are rather thin and some minor cross-threading and grinding was encountered during tests.

Output: The ET10 has a simple 2-mode operation activated by twisting its head. When tightened all the way down, the lights switches off. Loosened 1/8 of a turn activated the Low (3 lumens) mode, another 1/3 of a turn activated the High (50 lumens) mode. Beam profile produced is almost purely flood, which is the natural characteristic from the bare XP-E LED used. I find this more practical and useful compared to those with sharply defined hotspots as far as key chain lights are concerned. There is a slight discernable hotspot produced due to the shallow polished cup in the bezel. Beam temperature is slightly cool, with a slightly warmer central area.

Output intensities of the ET10 are rather conservative which is good considering that it's running on a single AAA battery. The instruction sheet states that the High modes drives the LED at 150mA while Low is 10mA.

Level	Low	High
Lumens	3 Lumens	50 Lumens

Runtime Plot: The trade-off to this lower output is obviously longer runtime, but more importantly it also allows the ET10 to maintain tight regulation which rare among single AAA powered lights. The ET10 does not support 3.7C 10440 cells.

Batteries: For batteries, this light is approved by the manufacturer for use with AAA alkaline.

What I Liked: Very well built and good exterior finishing. Above average runtime and tight regulation.

What I Didn't Like:Some cross threading and grinding on threads.

Picky Little Things: Beam profile is almost purely flood with a very subtle hot spot. Color temperature is slightly cool. Uses a twist switch. Is able to tail stand.

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