Cometic Pontiac 326-455 CI V8 .043in Copper Exhaust Manifold Gasket Set - 2.000in x 1.550in D-PortsCOMETIC MLS (Multi Layer Steel) Head Gaskets provide maximum sealing performance for todays high output engines and require no sealants. MLS gaskets are ideal for both aluminum heads to aluminum blocks and aluminum heads to cast iron blocks. They can withstand the shearing force created by the two materials. MLS gaskets have increased strength because they are comprised of multiple layers of stainless steel; which also creates the ability to rebound