The assembly does not include the rubber carb boot or the O-ring (BS 026), both are available for separate or bundle purchase.
The O-ring sealing surface location is set at 31 thru 36mm diameter (check that you have a good flat sealing surface at this diameter).
This mounting flange is designed for fitting Mikuni carburetors with a 35mm spigot outside diameter to any engine with mounting stud spacings ranging from 46mm centre to centre measurement through to 75mm. The alloy stub flange is made using 6061 grade Aluminum with a silver anodized coating. The inside hole diameter is 28mm with a total height of 28mm and 35mm outside spigot diameter for matching with Mikuni VM24 thru VM28 Roundslide carbs, TM Flatslide carbs with 35mm or close size spigots or other such applications. The slotted mounting holes in the 10mm thick base do suit mounting hole centres from 46 thru 75mm when using up to 5/16″ or 8mm socket head screws (Allen key).