The Dwyer VP1 Wired 100 mm Vane Thermo-Anemometer Probe with Coiled Cable for Model 473B measures air velocity, air flow, humidity, and temperature when combined with Model 473B. By having a larger diameter, the rotating vane is able to measure velocities down to 50 fpm or 0.25 m/s. An arrow is molded into the vane housing to depict the flow direction.