Hmmm, nice response there Jeff.Ok, let me try:There is a standard of inner venturi sizes that differentiate between a set make/model of carburetors irregardless of design e.g. flat slide/ round slide, butterfly, etc...that come standard equipped but can be altered according to manufacturer availability or customized by the end user (mikuni, solex, weber, delorto...) or are caste (i.e. flat/round sl