Model "3171" Back Pressure Relief Reg.,Clean Per Cashco Spec #S-1576; 1/2" Size; 316l SST Body & Cf3m Spring Chamber; S1l Trim: 316l SST Metal Seat, 302SST Diaphragm; Tri-Clamp Fitting Connection; 5-30 PSIG SST Range Spring; Wetted Parts Cert 'U' (Usp Class Vi)