A receiver groove is machined into the deck surface of the heads and our USA made stainless wire is pressed into the groove- the wire protrudes from the groove applying extra pressure to all layers of the gaskets- sealing combustion pressure in the cylinder. It is reusable should you have the heads off of the engine for any reason in the future. Our o-ringed heads work with any standard off the shelf head gasket. WE do not require any special machining of the block just prep the deck surface ensuring the block is clean dry and flat. The O-ring provides a heat sink from the fire ring and conveys that heat obtained into the cooling system.