This is a CNC induction collar for large bore carburettors such as Dell'Orto VHS 34mm-39mm, Dell'Orto PHBH 28-30mm, Mikuni TMX 35mm, Kehin PWK38mm etc. Sold singularly, with a cchoice of six anodised colour options. Comes supplied with 2 sets of small Allen screws for fixing to the carb. The internal diameter is 64.2mm. Made from high grade Ergal, these collars are based on those used on the Casa Lambretta Racing Team scooters. Although these were initially designed primarily as a custom part, rather than a performance enhancement part, we have actually seen that max power putput is increased by 0.5bhp with one of these fitted to an engine! Please note that on some carbs it may be neccessary to remove (file away) the outer lip as indicated in one of the pictures for fitment of the collar. If you wish to fit the collar to a Dell'Orto PHBH carb, then you will need to utilise a plastic adaptor riNg X15b.