The Automation Components Inc. (ACI) 121996 Thermistor Duct is a temperature-sensing component with an 8-inch probe and protective enclosure, designed for HVAC duct applications. It uses a thermistor to detect changes in air temperature and provides a resistance signal to compatible controllers for monitoring and regulation. Commonly used in air handlers, rooftop units, ventilation sy... https://www.partshnc.com/automation-components-inc-aci-121996-10kohm-thermistor-duct-8-enclosure