Ultrasonic wind meter uses patented technology to read current wind speed, highest positive speed (headwind), lowest negative speed (tailwind), 5-second average, and running average. Select from mph, km/h, fpm, m/s, f/s, or knots, plus temperature and wind chill in tenths of °F or °C. Sensitive to breezes as low as 0.4 mph, yet withstands winds as high as 150 mph. Includes replaceable 3-volt lithium battery, lanyard and mounting bracket. Battery lasts up to 600 hours. Dimensions: 5" x 3" x ¾" (12.7 x 7.6 x 1.9 cm). Weight: 3½ oz (100 grams).