Original SCE Pro Copper Embossed header & manifold gaskets for Chevrolet, Cadillac & GMC LS1, LS2, LS3, LS6, LS7 & LQ9 Gen 3/4 Small Block with Large Port Headers or Stock Manifold. Port Size: 1.780″ I.D. Round; Gasket Thickness: .043″ Material: Embossed Copper. SCE Gaskets invented embossed copper exhaust gaskets and they are proven to insure leak-free, re-usable performance on aftermarket headers or stock iron manifolds. Hard multi-layer steel gaskets work fine on a factory-new manifold but SCE Pro Copper exhaust gaskets give you both properties needed for good sealing, conformity and strength! Also seals irregular, pitted or warped surfaces because the raised copper sealing ring conforms to the header or manifold. Designed, manufactured & packaged in the USA using pure, premium US copper. Package Contents: 1 Pair.