Model BQ Rev A Back Pressure Regulator, Graphite/NBR Gaskets; 1/2" Inlets,1/2" Outlet; Sales Kit B; Carbon Steel Body With Stainless Steel Spring Chamber; S5 Trim: 316 Stainless Steel With Metal Seat, Fluorocarbon Elastomer (FKM) Diaphragm; OPT-1+6: Differental Construction With Closing Cap