... 2-3/4"dia, stainless steel frame Part No. DescriptionRW-RG-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 compound 30"-0-250 PSI, connection back 1/ ... 3/4"dia.ring for front mounting, class 2.5RW-FRG-500Red pressure 0-500 PSI, connection back 1/4"SAE ...