Stops block leaks | Seals cracked cylinder heads and blocks | Repairs blown head gaskets | Dual Action 2 Part Formula — LIQUID CERAMIC: Liquid penetrates large and small leaks to form a seal actually harder than the original head gasket — REINFORCED FIBERS: Fiber additives lock together with liquid to increase strength and promote a permanent seal | Head Gasket Sealant is NOT COMPATIBLE with antifreeze and must only be added to the cooling system after ALL ANTIFREEZE has been flushed and removed. | Included components: Unit, Instruction Guide