Handheld anemometers are an excellent, portable tool for performing tests on HVAC system performance; however, large rotating vanes can prevent easy access to ducts. Dwyer's Model VT-300 Miniature Vane Thermo-Anemometer eliminates this problem. The VT-300 measures air velocity, air volume, temperature, and humidity inside air ducts. It includes a telesoping vane probe that is only 0.7" (18 mm) in diameter that allows for duct traverse measurements in ducts up to 20". The easy to use handheld gives users the ability to choose from a variety of engineering units.