This flashlight is really good for the price. Brightness is superb and when zoomed tele, the ray is well visible in the air at night! This might be of advantage, once the SOS-feature or signalling has to be used from a concealed place.
Due to contrucion with a single lens, some light will just hit the inside of the head and will be wasted, if the head is pulled to tele zoom. This will also reveal the micro-USB port covered with a silicone stopper. Through the port opning, a red and a green LED show charge status. Red means charging, green finished. The flashlight has to be switched on for charging, but main light will remain off until the USB connector is pulled. Charging stops at 4.2V battery voltage and charging current is 500mA at 5VUSB.
With every power cycle the mode is changed: hi, mid, low, strobe, SOS, though the SOS is a bit strange. Sometimes the S is just coded with two dots. The fact that the last used setting is not retained for but changed at next power-up is a bit uncomfortable, because one has to click several times before power-down until the mode before the one desired for next power-up is active.
No docuentation. I'd like to change a jumper, if there is one, or mod this thing for another driver. The LED module is separate from the charger part, with a screw-in thread and a center contact spring.