The Exposure RedEye Mk2 Threaded Body TraceR Bracket Light is powered by Smart Port and Smart Port+Technology from your front light, never buy a battery again.Designed for day and night time running, excellent side visibility for urban riding.Exposure RedEye Mk2 Threaded Body TraceR Bracket Light SpecificationsLight: Solid - runs from the front lightCable Length: 1.05 metresIncludes moulded bracket for seat postNew threaded end allowing for more versatile mounting options.