The MLS gasket is comprised of three layers of Stainless Steel. We use Stainless steel for increased strength. It's ability to rebound and corrosion resistance. The out layers of the gasket are embossed and coated on both sides with a flouroelastomer rubber based material (Viton) designed to meet the demands of a variety of harsh sealing environments, load conditions and surface finishes. The vition coating is heat resistant to 2500C or 4820F