The 407123 is a heavy-duty hot wire thermo-anemometer designed for professional HVAC and ventilation applications. It features a telescoping probe that extends up to 7 feet (2.1 m) with cable, allowing measurements in small openings and confined spaces such as HVAC ducts and vents. The instrument measures air velocity from 0.2 to 20 m/s (40 to 3940 ft/min) with 0.1 m/s resolution and ±3% basic accuracy, and temperature from 0 to 50°C (32 to 122°F) with 0.1° resolution and ±0.8°C accuracy. It includes a super large 1.4-inch (36 mm) dual LCD display with MAX/MIN and Data Hold functions, powered by six AAA batteries, and comes with a protective holster. The 407123 is ideal for HVAC technicians, building diagnostics, and environmental monitoring where precise airflow and temperature measurements in tight spaces are essential.