Model "BQ" Back Pressure Relief Regulator,Graphite/Nbr Gaskets; 1/4" Inlets,1/2" Outlet; Cf8m Body & Spring Chamber; Sb Trim: 316SST With Buna-N (Nbr) Seat, Buna-N (Nbr) Diaphragm.; Npt Screwed; 140-300 PSIG Range Spring; Opt-25: 1/4" Npt Spring Chamber Vent Tap