Dellorto Billet velocity stack that fits SS & SSI 27,29,30mm carbs. Stacks are nicely polished and measure 70mm long and 50mm at the widest part. Velocity stacks are bored to match carb size and not a one size fits all application. Please select the velocity stack size you need from the pull down menu. NOTE: Stacks only fit Dellorto SS & SSI carbs and will not fit on Mikuni, Kehin, Amal, Bing, S&S or other brands of carbs.