Manufactured from advanced phenolic thermoset plastic and engineered to withstand extreme high intake manifold temperatures, these spacers were designed to insulate and reduce heat flow to the carburetor keeping it cooler to allow a denser fuel mixture to enter the engine and produce more horsepower. Available to fit the standard Holley/Carter and Quadrajet four-barrel bolt pattern in your choice of either an open center or four-hole straight bore design, and are packaged complete with gaskets, studs, nuts, and washers. A must for any serious racing enthusiast.