Heavy duty centrifugal clutch 1"bore 10 tooth #41/420 chain. Rated up to 7hp. This fits on a 1" crankshaft the other end is 3/8". The end of the crankshaft must be drilled and tapped to accept a bolt to hold clutch onto shaft. Comes with two set screws and 1/4" key. This is a heavy duty clutch designed for standard live axle karts using up to 18" tall tires. This will not take the place of a torque converter, but is ideal for fairly flat land riding. The 10t sprocket allows you to achieve a desired gear ratio for good pulling power, recommend using at least a 60T drive sprocket. Others offer a 14T clutch that does not have near the pulling power needed. For larger tire application and extreme riding you will need a torque converter. Not available for #35 chain Dimensions- outside diameter 4 3/4" total width 3"