30 Series Torque Converters use 3/4" top width belts that are flat on one side and angled on the other. Drive clutches have both 3/4" and 1" bore. Driven clutches have either a 5/8" or 3/4" bore and use both 6" and 7" diameter pulleys. 30 Series clutches use a green tension spring in the pulley. They are used on many makes and models of go-karts and mini-bikes including Manco, Murray and Yerf-Dog.