This 3-piece stainless steel head gasket features an aluminized center sandwiched between two nitrile bunadine rubber (NBR) coated stainless sprng steel outer layers that are embossed. Drain back O-rings are not required. Fits Twin Cam 1999-later The rocker cover gaskets are made from an embossed stainless spring steel coated on both sides with NBR. The umbrella valves, intake seals and all O-Rings are made from either Viton or NBR. CFM-20 head gaskets are made from a perforated steel core laminated with a fiber type external material. They include a stainless steel fire ring.