GU81-50T40 American Water Heaters ProLine Master 50 Gallon Ultra-Low NOx Natural Gas Water Heater 8-year limited Tank warranty, 8-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.Enhanced-Flow Brass Drain Valve - Solid brass, tamper resistant, enhanced-flow, ball type, drain valve