... 250Blue compound 30"-0-250 PSI, class 2.5 connection bottom 1/8"NPT, 2-3/4"dia.RW-RG-500Red ... pressure 0-500 PSI, class 2.5 connection bottom 1/8"NPT, 2-3/4"dia.RW-FRG-250Blue ... connection back 1/4"SAE, 2-3/4"dia.ring for front mounting, class 2.5RW-250GFCompound filled glycerine 30"-0 ... -250 PSI, class 1.6 connection back 1 ...