This round style, pleated paper air filter provides great protection against the destructive effects of dirt ingestion. Used on select single-cylinder 20-21 hp engines, this OEM part ensures proper fit and performance to maintain the life of your BRIGGS & STRATTON engine. Not only are BRIGGS & STRATTON genuine parts assured to fit, but using them ensures that the BRIGGS & STRATTON engine they are installed on complies with applicable (EPA) emission regulations.