Mk III Handheld Digital Manometer is ideal for field calibration, monitoring or trouble shooting HVAC systems and a wide range of other low pressure pneumatic systems. Measures positive, negative or differential pressures in English and Metric pressure units. Dual push pads on front of unit with zero adjust knob on top. Includes instructions, 9-volt battery, low battery indicator, and pressure connections for 1/8" or 3/16" I.D. tubing. Accuracy 0.5%.