Mr. Gasket Performance Valve Cover Gaskets are high-density cork/rubber blend gaskets that use evenly sized cork particles distributed evenly throughout the rubber binder. The result is a compressible valve cover gasket without leak paths. These gaskets create a positive seal by controlled swelling of the gasket material when exposed to hot engine oil. Provides excellent flange sealing and durability. For original equipment replacement, high performance street, drag race and oval track use.