Air flow displayed in 5 measuring units (ft/min, m/s, km/h, MPH, knots). Min/max button with recall feature. Data hold freezes current value. Lightweight, easy to hold shape. Low friction ball vane wheel provides high accuracy at all air velocities. Auto power off after 10 minutes of inactivity. Specifications: Air flow range: 80 to 5910 FPM (0.4 to 30 m/s). Accuracy: plus/minus 3 percent full scale. Resolution: 1 ft/min (0.1 m/sec). Dimensions 6.15 x 2.36 x 1.29 in. Power source: 1 9 volt battery. Weight 5.6 oz.