Bradford White Ultra Low NOx Eco-Defender Safety System®, 30 Gallon Tall Residential Gas (Natural) Atmospheric Vent Water Heater. 6-Year Tank Warranty, 32,000 BTU/Hr. The "-264" indicates that this SKU comes with an Aluminum Anode Rod. The "-394" indicates that this SKU comes with a Top T&P Location. The "-475" indicates that this SKU was designed to operate in Altitudes between 2,001 feet and 7,000 feet.