... pressure gauge bottom brass connection diameter:1.5",2",2.5",3",4",6". Black Steel Case Dual Scale Dry Pressure Gauge 1 ... ;3.Window:glass, acrylic, polycarbonate;4.Internal: brass, stainless steel;5.Inlet thread:1/8", 1/4", 3/8",1/2", ... order.9.Oil composing:glyceine, silicone oil;10.Accuracy: 2.5%,1.6%,1%. Black Steel Case Dual Scale Dry Pressure Gauge