RPC Phenolic Plastic Carburettor Spacer, Open Center, 2" Spacer (RPCR9137)PHENOLIC CARB 2" SPACER Fits Holley AFB Four Barrel Carburettors, Gasket & 3" Stud Kit Included Part Number: RPCR9137 Made out of phenolic resin and engineered to reduce heat transfer from the intake manifold to the carburetor that provides a denser air fuel mixture for increased power and efficiency. Includes mounting hardware and gaskets for a no hassle installation. Specifications: 2" Thickness Fits Holley 4150 4160 4BBL Carburetor Flanges Includes