Mr. Gasket Ultra-Seal Collector Gaskets feature a steel core for strength and a graphite-impregnated material that resists heat and pressure. Gaskets conform to the flange for a superior seal. The inside diameter of the gasket is 2.75". The graphite means the gaskets are easier to remove, too. Ultra-seal gaskets are reusable. Hardware is not included with this kit. Ultra-seal collectors gaskets are sold as a pair.