Addendum:
After a few months, the third battery change the mechanics of the battery compartment is broken. Only two small plastic tabs holding the battery compartment with springs tensioned together. One of them has adopted itself - the lamp is thus actually over, but this can be a makeshift kitten with cable ties. The taillight has proved in practice on the road clearly as too dark. In addition, it is covered with many jackets from the hood. Hoods are also the ones that confuse the sensor, which quickly leads to go out of the light and in normal running.
In road traffic, the rear light is rather useless and outdoor applications generally works only when wearing no hood. The lamp comes in handy for house and home, and the sensor at Yourself in the basement or dark corners. This same technology is outdoor but undoing. Due to poor design or to brittle material on the battery compartment, I can not recommend to buy the lamp, however.
