Product details:

The Wireless Indoor Sensor(s) is used to change the sensing location of the thermostat - Works with RedLINK 2.0 thermostats - Sense temperature and humidity remotely - Average temperature - Control temperature and humidity in separate locations - Humidify and dehumidify in separate locations. For example, humidify on the main level and dehumidify in the crawl space - Up to 6 Wireless Indoor Sensors per thermostat - Includes: 2 AAA alkaline batteries and mounting hardware