Model "BQ" Back Press Relief Regulator, Tfe Gaskets; 1/2" Inlets,1/2" Outlet; Bronze Body & Spring Chamber (Opt-5), Cryogenic Construction;Opt-55: Cleaned For Oxygen Service Per Spec #S-1134; B1 TRIM: BRASS METAL SEAT, 302 SST DIAPHRAGM; Npt Screwed; 65-150 PSIG SST Range Spring