270000 Btu/hr Heating, Natural Gas, 3/4 in IPS Gas Connection, 100 gal Tank, Spark Ignition, 6 in Vent Size, 264 gph at 100 deg F Rise Recovery, 80.4 % Energy Efficient, 1-1/2 in IPS Water Connection, 180 deg F, Ultra Low NOx: Yes, ASME Yes/No: No, Steel, 72-5/8 in OAH (Price subject to change without notice. Check stock before order)