The OEM Briggs and Stratton Lawn Mower Air Filter ensures proper fit and performance to maintain the life of your Briggs and Stratton engine. Many engine performance problems can be linked to maintenance issues such as stale fuel, a dirty air filter, fouled spark plug, and deteriorated oil. A great way to help avoid these problems is to perform an annual tune-up. Your outdoor power equipment's engine air filter provides superior protection against the destructive effects of dirt ingestion. for 450e, 500e, 550e and 550ex Series with a foam mower air filter, this Briggs and Stratton lawn mower air filter replacement part ensures proper fit and performance to maintain the life of your Briggs and Stratton engine.