Siemens 254-01117 Zone Control Valve Assembly ANSI 250, 2-Way Normally Open, Linear, 1/2-Inch Female NPT Connections, 0.63 Cv, 200N, Electro-Mechanical Two-way zone control valve SSB81U 3-position, Fail-in-Place Actuator Female NPT connections and brass trim ANSI Leakage Class IV 0.63 Cv flow rate