The A.J. Antunes 8023202259 Differential Pressure Switch is a non-adjustable air pressure monitoring device with a factory-set activation point of 0.15 inches water column (W.C.) and convenient barbed fittings. It detects pressure differences and activates an electrical switch when the preset threshold is reached. Designed for HVAC ventilation systems, air handlers, ductwork, fans, an... https://www.partshnc.com/a-j-antunes-8023202259-differential-pressure-switch-0-15-wc-w-barb-fittings