RK Racing Chain 1022-048S Steel Rear Sprocket and 520MXZ4 Chain Steel Race Kit Fits: Honda CRF250R 04-09 Steel race kit contains: 13 tooth chromoly front sprocket; 52 tooth steel rear sprocket; and RK 520MXZ4-116 link chain MXZ4 chains are made for the serious motocross racer looking for the lightest, strongest, non O-ring chain MXZ4 chains feature chromoly steel construction with seamless rollers and bushings, and oversized special alloy pins for added strength All components of the MXZ4 chain are heat treated using RK's exclusive HIT (Heat Induction Transfer) process and include a clip type master link