The STA2 is a Hot-wire Anemometer built for the HVACR professionals' air balancing needs. The compact probe tip makes measuring air velocity directly in the duct a breeze. It's great for traversing a duct and automatically calculating CFM without the hassle and expense of a bulky hood. The 38? telescoping probe's laser etched ruling and flattened edges allows techs to locate proper measurement points within a duct, and ensures that the probe is properly aligned.