TSI AirPro VTH-S Velocity Temperature Humidity Straight Probe for AP500 Bluetooth Air Velocity Meter is for use with the TSI Air Pro AP500 Velocity Meter. The TSI AirPro VTH-S attaches to the AirPro AP500 and measures air velocity, temperature, and humidity with the ability to be extended with 800529 Probe Extension. The TSI VTH-S is 12 inch in length and measures air velocity from 30 ft/min to 6000 ft/min, temperature from 14°F to 150°F (-10 to 65°C), and humidity from 0 to 95%.**Requires TSI AirPro AP500**