This is a genuine Briggs Stratton gas fuel cap, model number 397974S, made of durable plastic. It is designed to fit most Briggs Stratton lawn mowers and is a necessary part for maintaining the efficiency of your mower. The cap is made specifically for gas-powered mowers and is easy to install. With this high-quality gas cap, you can be sure that your lawn mower is running at its best. The cap is designed to fit securely and provide a reliable seal for your mower's fuel system. It is a great replacement part for your Briggs Stratton lawn mower and is sure to keep your mower running smoothly for years to come.