The TSI Alnor 800219 temperature and humidity probe is a telescopic probe extending from 9 to 39 inches (230 to 990 mm) and is ideal for measuring the inside of ductwork before and after a coil. This TSI Alnor probe can be inserted into a standard 5/16 inch (8 mm) diameter hole and is designed for use with the EBT721 balometer. Typically used for pitot traverses, the 800219 probe can also be used to calculate wet bulb and dew point temperatures.