This rubber flange adapter allows you to change your carburetor from a flange mounted carburetor to a spigot mounted carburetor. It is for carburetors with about a 35mm OD spigot. Note: This is not the carburetor size, but the spigot size. The inside diameter at the manifold side is 26mm, but it can be opened up to 28mm. The center to center measurement for the bolt or stud holes is about 2 inches (45-52mm). Holes are made for 6mm or 1/4" studs or bolts, but these holes can be drilled open for 5/16th or 8mm bolts.
We often use these to use PWK style carbs with our Minarelli Vertical VM20 intakes.