"Hilliard Extreme-Duty clutches are ideal for the everyday demands of go-karts and youth-model snowmobiles. Thermodynamically designed clutch shoe increases the clutch's capacity to absorb heat without damaging the clutch springs, thereby providing a longer service life, even in the most demanding applications. For use with engines up to 13 HP. No warranty. Returns on unused product only. U.S.A. Bore Diameter in. 3/4, Overload Protection Yes, Application Sprocket, Teeth qty. 13, Chain Type #35, Engagement Speed RPM 2,300, Engine Up to 13 HP. Bi-directional operation Load-free starting Overload protection Easy to install Integral key design Replaceable sprocket Easy-to-change springs Tolerates excessive heat generated by inexperienced riders, riding with one foot on brake, riding in soft dirt and tall grass, and frequent starts and stops"