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 inch 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. made in United States. Manufactured by Fieldpiece instruments Inc.