Model "1164" Back Pressure Relief Regulator,Aramid/Sbr Gaskets; 1-1/2" Size; Ductile Iron Body,Cast Iron Spring Chamber; S5 Trim: 316SST Trim With Tfe Seat,Phos.Bronze Diaphragm; Npt Screwed; 10-40 PSIG Range Spring; Opt-25: 1/4" Npt Spring Chamber Vent Tap