IAG Performance Fire Lock Head Gaskets 93.5mm Bore 1.3mm Thickness PAIRThe IAG Performance Fire Lock head gasket solution was created after years of research and development testing to prevent head gasket failure on high horsepower and high boost Subaru EJ Series engines. This solution is loosely derived from diesel technology where a counterbore step is machined around each cylinder bore allowing specially sized fire rings to drop into the machined area and head gasket bores. The shims are designed to create a