The Dwyer VP3 Vane Thermo-Anemometer Probe, 100 MM measures air velocity, air flow, humidity, and temperature when combined with the Model UHH6 Universal Handheld. The VP3's rotating vane is bale to measure velocities down to 50 fpm or 0.25 m/s. An arrow is molded in the VP3 housing to depict the flow direction.