api 5000API 6A6B6BX FLANGE STANDARD, Class 2000PSI, 3000PSI, 5000PSI, 10000PSI, 20000PSI,data sheet including OD, ID, Thickness, Neck dimensions, bolt holesAPI has specified weld necks for many 6BX flanges, and not done so for many others, but API has provided the basis for determining the dimensions of a 6BX integral flange