The 407119 Heavy Duty CFM Hot Wire Thermo-Anemometer has a telescopic probe (up to 3 ft) that is suited for use in ducts and ventilation systems. It accurately measures air flow (CFM/CMM), velocity, and temperature. Air flow can be presented as an immediate figure or as a 20-point average. Additional features include Data Hold, Min/Max, and Auto Power Off. The kit includes a telescoping probe with a 5.5-foot wire and four AA batteries.