The R-Type Ring Gasket is found in two shapes, Oval or Octagonal. Both shapes have the same pitch diameter as the flange groove they communicate to. These gaskets are used in pressures up to 10,000 PSI. Both the Gaskets can be used in Flanges with flat bottom v-grooves.
RX Gaskets are designed for pressures up to 15,000 PSI. These gaskets are compatible to R Type Oval or R Type Octagonal rings used on API 6B flanges. Thickness or the height of these RX type of gaskets are more than R type gaskets, hence the weight of one ring is also more than Rtype gaskets, therefore it is expensive when compared to Rtype gaskets.
BX Gaskets are designed for pressures up to 15,000 PSI. These gaskets are compatible to R Type Oval or R Type Octagonal rings used on API 6B flanges. Thickness or the height of these BX type of gaskets are more than R type gaskets, hence the weight of one ring is also more than Rtype gaskets.
BX Ring Gasket is distinct from the oval or octagonal gasket. The gasket is square in cross section and it is tapered at each angle. BX is used at pressures up to 15,000 psi and it can be used only in API 6BXflanges and 16BX hubs.