.027" MLS (multi Layer Steel) head & .014" RCS (Rubber Coated Steel) base gaskets. 4.500" bore. For water & oil cooled heads. Heads must be plugged. No embossing on heads for water or oil cooling ports but for bore & oil drain only. Therefore heads must be plugged or welded in all cases. Kit to service one engine. / Fitment: Custom 17-25 M8 4.500" big bore models with plugged heads