Square Port header gaskets for Chrysler B and RB big block engines, covering 1959–1980 383, 400, 413, 426 wedge, and 440 applications. Built with a high-temperature steel core for strength and long-term torque retention, these gaskets feature a graphite facing that conforms to minor flange irregularities and helps transfer heat away from the cylinder head. The surface is coated with high-temperature silicone to enhance sealing performance, and the material will not imprint or mark aluminum cylinder heads. Can be trimmed for modified port shapes when required. Suitable for OE replacement, performance street engines, drag racing, and oval-track use.