Speed Factory Racing 4-layer Stainless Steel Head Gaskets come with specialized embossments that increase combustion sealing height to ensure the gaskets withstand the high levels of combustion, lift, and movement of high-performance engines. The internal silicone bead on the oiling passages improves sealing and eliminates oil leaks. The thickness is ideal for use with o-rings, which are mandatory for reliable combustion sealing. The design is compatible with 1/2" head studs, allowing for easier engine assembly. With all the features combined, the gaskets have been tested on Bullet Billet Blocks at 1400+whp.