Style RX is a pressure energized adaptation of the standard Style R Ring Type Joint. As the RX is designed to fit the same groove design as a Standard Style R, the joints are interchangeable. Style RX gaskets are designed for pressures up to 15000 psi. These gaskets are interchangeable with r-oval or r-octagonal rings used on API 6B flanges.
Style RX is more costly than your standard oval or octagonal rings, therefore not as popular. Style RX perform excellent in 6B flanged blowout preventer stacks, which requires the additional mass of the RX to support the higher pressures with higher vibrations and heavier weights of these units.