The Siemens 656-0018 3/4" Angle Union Valve is a normally open, pneumatic control valve with a 4.6 Cv rating and 3–8 PSI operating range. Designed for precise modulation of hot or chilled water flow, it is commonly used in HVAC systems such as fan coil units, air handling units, and terminal reheat applications. https://www.partshnc.com/34novlv38angle-46cv