The BBR Tuning Adapter is a durable aluminum unit that provides fast and easy installation when used with the BBR Tuning Sprocket. Unlike the traditional sprocket clamp assembly, the BBR Tuning Sprocket and Adapter Assembly ensure concentricity with the wheel hub by using the unique two-piece adapter that wraps around the rear wheel hub and enables you to drive the entire wheel instead of applying pressure on the spokes. ADAPTER ONLY, DOES NOT INCLUDE THE SPROCKET.