API Specified 6B Weld Neck Flanges have restricted bores to match standard pipe sizes and schedules. API Spec 6A Specified, 6 BX Weld Neck Flanges, have material and dimensions that conform to the requirements for full bore integral flanges. API Spec 6A does not specify overall length of 6BX Weld Neck Flanges, but instead provides dimensions of specific portions of the flange, with tolerance, that are added together, along with an undefined weld bevel, to achieve a length. Customers may specify weld neck length if required.  

API Specified 6B Weld Neck Flanges have restricted bores to match standard pipe sizes and schedules. API Spec 6A Specified, 6 BX Weld Neck Flanges, have material and dimensions that conform to the requirements for full bore integral flanges. API Spec 6A does not specify overall length of 6BX Weld Neck Flanges, but instead provides dimensions of specific portions of the flange, with tolerance, that are added together, along with an undefined weld bevel, to achieve a length. Customers may specify weld neck length if required.