ISO 7241-B lays down the interface dimensions and specifies basic performance requirements for two series of general-purpose quick-action couplings. Both series are in widespread use and have similar technological advantages. The distinction in usage is mainly geographical. Series “A” (covering sizes 6,3 to 50) is used predominantly in Europe and series “B” (covering sizes 5 to 50) is predominant in America.

Source: International Organization for Standardization