Rheem PROG50-38N RH58 Professional Classic Tall Residential 38K BTU Atmospheric Natural Gas Water Heater, 50-Gallon Low Emissions: Eco-friendly burner, low Knox design, Meets 40 ng/J Knox requirements Rheum exclusive R-Tech (registered) anode rod provides long-lasting tank protection Easy to light - no matches required. EverKleen patented system fights sediment build-up Enhanced-flow brass drain valve - Low lead compliant This new Model number replaces the old Model number 22V50F1