This flywheel key can be used as a replacement part for small engine lawn and garden equipment, including lawn tractors, lawn mowers, snowblowers, leaf blowers, vacuums, and tillers. The function of a flywheel key is to connect the engine's flywheel to the crankshaft, relative to the piston. Flywheel keys can often suffer damage in the form of shearing as a result of the engine being stopped abruptly. Even a little bit of shearing of the flywheel key will prevent the engine from starting properly or maintaining its power and fuel economy; a shorn off flywheel key might cause the engine to misfire or run rough. If this kind of damage occurs, the flywheel key must be removed and replaced immediately. Remember to always wear gloves when handling, repairing, and operating outdoor equipment. This flywheel key is a genuine OEM replacement part sourced directly from the manufacturer. It is sold as an individual component. The flywheel keep is compatible with the following brands: Tecumseh, Briggs & Stratton, Toro, and Craftsman.