Specification: Item Type: E Bike Motor Gear Clutch Kit Material: Steel + nylon Nylon Tooth Belt Size: Outer Diameter: Approx. 47.5mm / 1.87in, Inner Diameter: Approx. 8mm / 0.31in, Thickness: Approx. 13.5mm / 0.53in Clutch Size: Outer Diameter: Approx. 88mm / 3.46in, Inner Diameter: Approx. 15mm / 0.59in(manual measurement allowable error) Nylon Gear: 36T Applicable Motor: 500W Package List: 1 x E Bike Motor Gear Clutch Kit Note: Pay attention to the size of the motor.