American Water Heaters BFG61-40S40-3NOV Natural Gas Residential Short Water Heater, 40 Gallon Non-CFC Polyurethane Foam to prevent heat loss and reduce energy costs Piezo Electric Igniter for easy start-up Fused Ceramic Shield Tank for anti-corrosion protection Factory Installed Side Temperature and Pressure Valve Combination Thermostat/Energy Cut-Off