What is the difference between the MACE PERFORMANCE MANIFOLD INSULATOR KIT for VS–VT and VX–VY Commodores?

The profile between the two insulators in these kits is different to take into account the different PCV port designs for each inlet manifold type. To clarify which insulator fits which engine, MI601 is suitable for VS-VT Commodore Ecotec engines while MI602 is suitable for VX - VY Commodore Ecotec engines.