The ROOT!T Thermostat is an electronic device that allows you to maintain the temperature of the root environment by switching the ROOT!T Heat Mats on and off. It ensures that a consistent temperature is achieved that can be set above 20˚C. TIP: Use the ROOT!T Thermostat to extend the growing season. Put the heat mat on a timer in the morning and evening so that the plants experience spring day temperatures. Ideal for use with the ROOT!T T5 Light Strip and Reflector to give true spring conditions.