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.