TPI 610 Single Input Digital Manometer, +/- 80 inH2O Measuring Range, +/- 0.5% Accuracy, 0.01 inH2O Resolution, One Unit of Measure, Battery Operated Digital single-input manometer measures pressure and vacuum in HVAC testing 1/4" barbed connection for use with dry, non-corrosive air and gas + or - 80 inches of water measuring range and + or - 1% of full scale accuracy Measures in inches of water Built-in hanging hook and magnets provide hands-free use, auto-ranging provides accuracy at low pressures, trim mode smoothing function stabilizes erratic readings, zero function provides field calibration and automatic power-off extends battery life