Model "BQ" Back Pressure Relief Regulator,Graphite/Nbr Gaskets; 1/4" Inlets,1/2" Outlet; Cf8m Body & Spring Chamber; S40v Trim: 316SST With Fluorocarbon Elastomer (Fkm) Seat & Diaphragm; Npt Screwed; 20-75 PSIG Range Spring; Opt-25: 1/4" Npt Spring Chamber Vent Tap