The Groen 12313 K-Type Thermostat regulates heat by sensing temperature through its coiled bulb and translating that change into mechanical switching at the control. When the sensed temperature reaches the selected setting, the thermostat changes the heating circuit state; as the temperature drops, the contacts switch back to call for additional heat. The 8-inch coiled sensing bulb co... https://partsfe.com/12313-groen-thermostat-k-8-coiled-48