1 inch spread-bore carb spacer, it is pilot drilled for both spread bore and squarebore. The adapter is sand cast aluminium and is a linished finish on both carb and manifold face. It will require which ever Holley spreadbore & Rochester 4 barrel carburetor stud holes to be drilled.
You can also counter bore it so you can used it as an adaptor or drill straight through as a spacer. We have other carb spacers in our online speed shop for 2 barrel and 4 barrel squarebore carburetors. Note This spacer can not be used with 450 Spreadbore Holley Econo style carburettors with the 4 butterflys the same size.