There are four types of ring joints, or in other words ring gaskets, RX, R and BX. These gaskets are generally used at high pressures up to 20,000 PSI, which require special grooved flanges.

Type R is available in 2 types of octagonal and oval cross-sections. The octagonal gasket has a higher sealing efficiency than the oval one, and hence it will be the preferred gasket.
However, only an oval cross-section can be used in the old-style round-bottom groove flange, and the newer flat-groove design flanges accept oval or octagonal cross-sections. The sealing surfaces on the grooves of the rim connection should be smooth and at least 63 micro inches, and in order to prevent damage to the flange surface, it is always recommended that the hardness of the ring gasket material be about 30 brinells less than the hardness of the flanges used. The maximum withstand pressure of this type will be up to 2500 PSI.

Another type of these washers is the RX model, which is used in higher pressure conditions and generally up to 5000 PSI class.The last type, the BX model, is used for very high pressures up to 20000 PSI class and is mainly used in wellhead equipment.

This type of gaskets can be made with Inconel 825, Soft Iron, SS304, SS316, Titanium materials and even with special grades of steel.

The sizes of this gasket are from ½ inch to 60 inches and its standard ID is from R12 to R105.

The reference dimensional standards for making these washers are ASME B 16.20 and API 6A.