The RX type RTJ gasket is manufactured in accordance to API 6A and ASME B16.20 to suit API 6B and ASME/ANSI B16.5 flanges. The RX is a pressure energized version of the R octagonal gasket and fits the R type flat bottomed groove.

The RX has an increased height and utilises the internal system pressure to energise and improve the seal as internal pressure increases. Some RX sizes have a pressure relief hole to equalise pressure both sides of the sealing faces.