... diameter:1.5",2",2.5",3",4",6". Bottom Brass Connection Stainless Steel Oil Filled Pressure Gauge 1. Diameter: 1 ½", 2 ... .Internal: brass, stainless steel;5.Inlet thread:1/8", 1/4", 3/8",1/2",NPT,BSPT,BSP;6.Connection: bottom connection, center ... , silicone oil;10.Accuracy: 2.5%,1.6%,1%. Bottom Brass Connection Stainless Steel Oil Filled Pressure Gauge