GU61-40T40R American Water Heaters ProLine 40 Gallon Ultra-Low NOx Natural Gas Water Heater6-year limited Tank warranty, 6-year parts warranty for Residential applicationsIntelligent Control Logic - The internal microprocessor provides enhanced operating parameters and tighter differentials for precise sensing and faster heating response to optimize performance.Green Choice® Gas Burner - Patented eco-friendly Ultra-Low NOx gas burner gas burner complies with SCAQMD Rule 1146.2 and other Air Quality Management Districts with similar requirements for NOx emissions of less than 10 ng/jCoregard™ Anode Rod - Our anode rods have a stainless steel core that extends the life of the anode rod allowing superior tank protection far longer than standard anode rods.Blue Diamond® Glass Coating - Provides superior corrosion resistance compared to industry standard glass lining