304 stainless steel case center back male connection oil composing:glycerine, silicone oil diameter:1.5",2",2.5",3",4", ... 6". Panel Mount Stainless Steel Liquid Filled Glycerine Pressure Gauge 1. Diameter: 1 ½", 2", 2 ½ ",3",4",6 ... .5%,1.6%,1%. Panel Mount Stainless Steel Liquid Filled Glycerine Pressure Gauge