api5000The API 6A specification is a standard developed for the American Petroleum Institute and shares many characteristics with ASME flanges. They are similar in dimensions, but their minimumAPI 6B API 5000 (Class 1500) 1-1316″ to 26-34 Pressure Class API 2000 (Class 600) API 3000 (Class 900) s Material Class BB Raised Faced& CC DD & EE Bolts Holes 4 to 48 Face Ring