Siemens 257-02039 Valve Assembly ANSI 250, 2-Way Normally Open, Modified Equal Percentage, 1/2-Inch Female by Union Male, 2.5 Cv, 3 to 8 Psi Spring Range, Pneumatic Two-way zone control valve 2-inch, 3 to 8 psi Pneumatic Actuator Female by union male connections 2.5 Cv flow rate Modified equal percentage