The Nordyne 663864R Low Side Service Valve, 3/4 inch, is a precision-engineered component used in HVAC refrigeration systems to control refrigerant flow and enable safe system servicing. Installed on the low-pressure side, it allows technicians to monitor, charge, or evacuate refrigerant efficiently. https://www.partshnc.com/663864r-nordyne-34-low-side-service-valve