The Brompton Rear Dynamo Light has an integral reflector and as such replaces the rear reflector on the bike. The rear light has a "stand light / safe stop" function which means it stays on for approximately 4 minutes after you stop.  The light is connected to the power of the hub dynamo via the front light (the front light connects to the dynamo and the rear light connects to the front light). Compatible with bikes with and without rear rack.