Bradford White Ultra Low NOx Eco-Defender Safety System®, 40 Gallon Standard Residential Gas (Natural) Power Direct Vent Water Heater. 6-Year Tank Warranty, 40,000 BTU/Hr., 120 Volts, Single Phase, with Power Cord included. The -264 indicates that this SKU comes with an Aluminum Anode Rod. The -475 indicates that this SKU was designed to operate in Altitudes between 2,001 feet and 7,000 feet.