Cometic Gasket EST Top End Gasket Kit - 66mm Bore C3187 EST (Extreme Sealing Technology) gasket kits include embossed stainless steel head, base and rocker gaskets covered with a proprietary rubber material Head gasket material allows heat to be drawn away from the combustion ring and dissipated evenly across the gasket surface to eliminate hot spots and gasket failure Sets contain all the necessary gaskets, seals and O-rings to rebuild the top end from the cylinder base upward