This Anemometer/Thermometer is especially useful for fume hoods because unlike conventional twisted vanes, the specially designed vanes on this probe give identical readings whether the airflow comes from the front or the back. The sensitivity and balance of the low friction bearing enables measurement of even the weakest air currents. Results can be displayed in your choice of meters/second, feet/minute, km/hour, or knots with an accuracy of +/-2% + 1d FSD. The large display also indicates air temperature in °C or °F and low battery. Hold function freezes results. A 9V battery and carrying case included. 6 5/8" x 3 1/4" x 1 1/4", 11.5 ounces