This is a rear bike light which has a brake detection function. It switches to a brake light mode when it detects that you are slowing down. It will also turn on automatically when it gets dark. In lighter conditions the rider can opt for a flashing mode and a breathing light mode. They are waterproof which means that you do not have to worry about them when it is raining even if it is really hard. It charged using USB and can therefore use a variety of different USB charges to charge it up. It can be installed in different positions, under the seat, on the vertical tube or any other suitable place as it has a flexible design.