COMETIC MLS (Multi-Layer Steel) Head Gaskets provide maximum sealing performance for today's 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.
We recommend running .5mm over your actual bore size.
4P 90 and 90.5mm Cometic Gaskets are an exclusive design pattern that puts the sealing ring in the proper place for those large bore sizes. You cannot buy these anywhere else, so if you are buying a large bore gasket like that from someone else then you are getting one made with tooling that was designed for the smaller bore sizes and it will not have the same sealing power as the 4P gasket.