The Honeywell Thermostat Subbase Q539K 1005 2 is a round-shaped programmable thermostat designed for electric power source heating and cooling systems. This model is specifically compatible with other Honeywell thermostats and is equipped with heat, cool, and off system switching options. With its reliable brand reputation and precise control features, this thermostat subbase is an essential component for maintaining optimal indoor temperatures in your home. Plus, with free shipping included, it's a convenient and efficient upgrade for your heating and cooling system.