High quality "NTC" type air temperature probe manufactured by Bosch. Overall length of 49mm, and a fitting thread of M12 x 1.5mm pitch. The resistance of the sensor changes with temperature. For direct connection to the DL1 a "pull up resistor" is required. If the sensor is ordered with a cable, this resistor is already included and will be ready for immediate use with the DL1 or DL2.