Adjusts burner firing patterns and average boiler water temperature to match system heat load // Reduces fuel consumption 10 to 20% // For use with new or existing residential boilers up to 300,000 Btu // Compatible with oil, gas and propane burners // Easy installation Sensor and wiring connections at the boiler; no outdoor sensor required Specification: Description : Single-Stage Universal Replacement Kit // : 3.85 / Shipping Width : 6.00 // Shipping Length : 6.10 // Shipping Height : 5.30