These homebuilder’s Lycoming Engine Valve Cover Gaskets replace the original cork gaskets that come standard on Lycoming O- 235, O-320 and O-360’s engines (sometimes referred to the parallel valve cylinder Lycoming). These Gaskets are molded from hightemperature silicone rubber and do not harden over time, so they can be reused again and again. This hi-tech silicone rubber offers a much lower compression set, so it is superior at maintaining an oil-tight seal for the life of the engine. They are not FAA approved and are not manufactured under a PMA. Used on parallel valve Lycoming engines O-235, O-290, O-320, O-340, O-360.