Simple design and outstanding durability. Easy to install and calibrate. A few plastic pucks and a spring control all the operating characteristics. Comes with a mounting bolt and cover puller bolt. Features blue spring. 4000 RPM engagement. 14 threaded. For use with 1-3/16" belt width. Specifically for Moto-Ski and Ski-Doo Rotax twins and high-performance singles '68-'75 and Alpine 640 thru '82. Original equipment fixed half clutch shafts thru '74 are round and measure 1-1/8” OD. '75-'82 models have a square fixed half clutch shaft. For 1-5/16” belt width models such as Alpine 640 '76-'82, belt spacer kit is required.