I bought these lights, one for me (UC02SS) and one for my wife (UC02). Previously I had an E01 light on my keychain, and found that the UC02 & UC02SS is a much more capable light for a few dollars more. It comes with a tiny rechargeable (USB) battery, and is a bright light for its size.
The battery is removable and replaceable, and the light turns on by twisting the top, with low first then high. It’s been dropped several times but keeps on ticking. It should also be able to take being submerged with an IP68 water rating. The SS version is heavier than the aluminum one, but they both feel solid. The stainless steel one I have is a little tougher to twist than the aluminum one. It also comes with a lanyard, which the aluminum version does not.
The 8 lumen setting works well for looking in small spaces and under desks for lost items, while the higher 130 lumen setting is great in a pinch, like while walking to the car in the middle of the night. When the battery is low, the high power setting is unavailable, which is the signal to recharge the light via USB.
It will not surpass my other lights & headlamps, but for having on you at all times, it’s great for quick checks into dimly lit areas.