Perm-Align SBC valve cover gaskets are specially designed and manufactured from 30 durometer 100% pure silicone molded over and vulcanized to a rigid steel frame. The extra-strength design will not leak, blow out or get sucked in like stock or inferior-quality aftermarket gaskets. Superior quality silcone/steel gaskets outlast cork and rubber composite designs to provide years of dependable service, especially when constantly removing and reinstalling valve covers. Oil resistant and a full 3/16″ thick. 2 Per package.