40 Gallon, Natural Gas Water Heater, 35,500 BTU's, 1" Insulation, First Hour Rating 67, 36 GPH At 90 Degree Rise, For Installations From Sea Level To 10,100', R-Value 8.00, EF.59, Draft Diverter Outlet Size 3" With Integrated Adapter For 4" Vent Option, Factory Installed T & P Valve, FVIR Approved, Stainless Steel Flame Arrestor,, Air Intake Entire Base Of Heater, Door Mounted Manual Reset TCO, Unit Dimensions 51-1/8"H x 20"D, 6 Year Tank & Parts Warranty, Not For Use In Mobile /Manufactured Homes, Models Built After 4-1-2011 Have Self Powered Honeywell Millivolt Generator Gas Control Valve.