API 600 Cast Steel Check Valves 1  SF-150 C.S. , Flanged Check Valves,Swing Type, API 600 ANSI Class 150 Size Range : 2"~36" 2  SF-300 C.S. , Flanged Check Valves,Swing Type, API 600 ANSI Class 300 Size Range : 2"~36" 3  SF-600 C.S. , Flanged Check Valves,Swing Type, API 600 ANSI Class 600 Size Range : 2"~36" 4  SF-900 C.S. , Flanged Check Valves,Swing Type, API 600 ANSI Class 900 Size Range : 2"~24" 5  SF-1500 C.S. , Flanged Check Valves,Swing Type, API 600 ANSI Class 1500 Size Range : 2"~24" 6  SF-2500 C.S. , Flanged Check Valves,Swing Type, API 600 ANSI Class 2500 Size Range : 2"~8"