Model BQ Rev A Back Pressure Regulator, Graphite/NBR Gaskets; 1/2" Inlets,1/2" Outlet; Stainless Steel Body With Stainless Steel Spring Chamber; S40V Trim: 316 Stainless Steel With Fluorocarbon Elastomer (FKM) Seat, Fluorocarbon Elastomer (FKM) Diaphragm; NPT End Connections; 20-75 PSIG Range Spring