When installing a new TSP CNC machined billet head, we highly recommend using all new o-ring seals and copper crush washers. This complete head gasket kit includes both inner and outer cylinder head o-rings, 1 water temp sensor o-ring, and 6 copper crush washers for the head bolts. Everything you need to propery install your new TSP cylinder head. We have sourced the highest quality VITON o-ring material desinged to withsatnd all engine compartment chemicals like gasoline, oil ,and engine coolant. VITON o-rings also have the highest heat range temperatures of any other o-ring material, allowing them to contiue to function at temps exceeding 400 degrees farenheit. VITON o-rings meet the manufatures recommended specifications for o-ring material.