This Honeywell Duct Mounted Temperature Sensor is a precision instrument designed for HVAC (Heating, Ventilation, and Air Conditioning) applications. The sensor features an 18-inch probe length and operates with a resistance of 20 kilo-ohms at 77 degrees Fahrenheit (25 degrees Celsius), which is the standard for this type of sensor. It comes with an enclosure to protect the sensor from environmental factors that could affect its performance. The sensor's primary function is to measure the temperature within ductwork and relay this information back to the HVAC system. This allows for accurate control of heating or cooling within a building, improving energy efficiency and comfort levels.