Just clip this light on your rear brake cable and it will help alert anyone behind you that you are slowing down Just clip this light on your rear brake cable and it will help alert anyone behind you that you are slowing down Functions just like a car brake light, illuminates when you begin to brake Compatible with U brakes, V brakes, canti`s, and mechanical disc brakes Rounded brass clamp screw will not harm or impeed brake cables or function Great addition to any light system, perfect for group rides 200 hours continuous light, average of approx. 250,000 braking processes 7g