The Cleveland Controls NS2-0112-00 Pressure Switch is a factory-calibrated low-pressure sensing device with a 0.25" WC set point, designed to monitor air pressure in HVAC systems. Its sensing diaphragm responds to positive, negative, or differential pressure and activates the integral snap-action switch when the specified pressure is reached. https://www.partshnc.com/ns2-0112-00-cleveland-controls-25-aaon-pressure-switch