Mr. Gasket Ultra-Seal Valve Cover Gaskets are made from a high-density and superior quality blend of cork and rubber gasket material with locating tabs. They are 5/16" thick and laminated with a steel core for extra rigidity. The steel core construction prevents the gasket from being drawn inside or pushed out of the engine at a high RPM. The valve cover builds a positive seal by controlling the swelling of gasket material when exposed to hot engine oil. A black latex rubber coating helps seal minor flange irregularities. Gaskets eliminate the possibility of oil leakage and are unshrinkable as well as non-sticky. Ideal for stock replacement use and are designed to suit high performance street race, drag race and oval tracks.