The Network Thermostat NT-DS is 2-Wire Duct Temperature Sensor with an 8" stainless steel probe. Designed to be used for Supply Air, Return Air, Walk-In Freezers, Refrigerated Display Cases, and countless other applications. The NT-DS connects to the J5T-x series of thermostats. Temperature Range: -40°F to +200°F (-40°C to +48°C)