BX 
The Ring Joint Gasket mainly used in high pressure, temperature applications in the petroleum industry. Mostly used for Valves, Pipes and Flanges. 
Type: BX, RX, R(Oval & Octagonal) 
Materials: Carbon Steel, Soft Iron, SS304, F5, 321, 304L, 316L, 316, 347. Or other materials according to your request. 

BX type ring joint gaskets are designed for BX flange grooves only, it is suitable for higher-pressure ratings starting at 2, 000 lbs and ending with 20, 000 lbs, incorporate a pressure balance hole to ensure equalization of pressure which may get trapped in the grooves. 
Spec.: BX150~BX303