This D&R Chassis Steel Driveshaft Adapter is for 1999-2007 Hayabusa. This D&R Steel Drive Shaft Adapter is CNC machined and broached and then case hardened to the same specifications and hardness as the OEM sprockets that come on the engines. The advantage to using a steel adapter over an aluminum, is that the steel is just like a sprocket, you can take it off and put it back on without compromising the integrity of the part, as well as not worrying about stripping the splines out of the center of the adapter. Please let us know if you need the Nut and Bend Over Washer. The Bend over washer is an additional $4.75 and the Nut is $10.00.