api5000API 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 that the manufacturer may attach to aAPI 6A - TYPE - 6BX 34.5 MPA (5000 PSI) Size OD C E1 G K T J1 J4 R BC N H Ring Number BX 13 58˝ 675 6 14.3 408.00 457 112.8 481.0 23.9 16 590.60 16 45