The ET180 Digital Differential Manometer from Klein Tools measures air and gas pressure for port 1, port 2, and measures the differential between the ports. Easily toggle between units: inH2O, bar, oz/in2, psi, mbar, kPa, inHg, mmHg, kg/cm2, ftH20, and cmH2O. Large, backlit LCD shows minimum, maximum and average values. Magnet on back for hands-free operation.