Style BX ring joint pressure energized gaskets are manufactured in accordance with API 6A and are designed for use on pressurized systems up to 20,000 PSI. When correctly fitted, the style BX gasket allows virtual surface-to-surface contact of the flange faces, which means that the gasket is fully trapped on both the inner and outer diameters. All BX gaskets incorporate a pressure balance hole to ensure equalization of pressure that may be trapped in the grooves. Although similar in style to the octagonal gaskets, the BX Series can only be used with 6BX flanges and 16BX hubs. Pitch diameters on BX gaskets are slightly larger than the pitch diameter of the flange. This forces the gasket to initially seal on its outside angles and secondly seal with its inside angles as the flange is bolted down to respective torque settings. Gaskets that have been torqued initiating a metal-to-metal seal should be discarded and not reused.