8mm Group Gasket is the thinner version to be used in new machines and those with very little wear. It is approximately 6mm thick on the outer edge and 8mm thick on the inner edge.
La Marzocco 8mm Group Head Gasket seals the Portafilter within the group head, in order to avoid leaks and heat loss. This gasket is compatible with Linea Classic, Linea PB, GB5, FB80, Strada (MP, EE, ABR, EP, AV) and GS3.
However, for Linea Mini, LEVA and KB90, they come with separate gaskets as standard.