The Resideo C7089R1013 RedLINK external Temperature and Humidity Sensor is intended for precise external temperature measurement in HVAC systems. This sensor, which stands 5" tall and 3.5" wide, uses a thermistor -40°F to 140°F and humidity levels ranging from 0% to 100% (non-condensing). It is vertically placed on the wall for simple installation and dependable functioning. https://www.partshnc.com/c7089r1013-resideo-wireless-outdoor-sensor