Cometic Gasket Inc. Exhaust Gaskets are designed to be used with manifolds or headers. Offered in a range of materials to make sure you are covered with any cylinder head and manifold/header combination. All exhaust gaskets are designed to be used without the use of messy sealants. Header Collector Gasket; Copper; 0.043 in.; 3.875 in. Bolt Circle; 3.0 in. Diameter Port;