Single Sprocket. Self Contained. 400 Series clutches have more contact surface than most competitors and built-in staying power. Almost 3 3/4in. squared of steel friction material engagement shoe surface assures positive pulling power as long as the RPM is in full contact range. There is no slipping when you need the go-power. 400 Series clutches have continued performance even when they were partly destroyed in torture tests. Bearings have been almost completely worn through by sand and the 400 Series continued to function. Pre-lubed clutch features a pre-lubed idler bushing, high temperature spring, zinc plated outer drum. Chain: 35. Teeth: 12. Bore: 1in.. Diameter: 4in.