... connection back 1/4"SAE, 2-3/4"dia, stainless steel frame Part No. DescriptionRW-RG-250Blue compound 30"-0-250 PSI ... back 1/4"SAE, 2-3/4"dia, stainless steel frameRW-250B-GFCompound filled glycerine 30"-0-250 PSI, class ... bottom 1/8"NPT, 2-3/4"dia, stainless steel frameRW-500B-GFPressure filled glycerine 0-500 PSI, class 1 ... connection bottom 1/8"NPT, 2-3/4"dia, stainless steel frame presurre gauge