U20 premium quality exhaust Seat rings. Made of a superior alloy over the originals which are iron. Composition: 42.0% Nickel, 7.5 % moly, 12.0% chrome, 3.0% silicon, 2.10% carbon, 2.0% vanadium remaining % iron & other elements. Sold as a set of 4.
The O.D. of these seats are slightly larger than stock to, .003 to .004, to allow for the proper press fit into the cylinder head.