~America's most popular floor furnace ~ The 3588 Empire Comfort Systems floor furnace provides total comfort for a fraction of the cost of electric heat.Needs no electricity to operate Matchless push - button piezo ignition Millivolt wall thermostat Whole - house heating capability Wall thermostat included with all units All parts carry a 3 - year limited warranty Proudly Made In USABottom of Unit for Air: 6 BTU Input: 32,500 Casing Length and Width: 32 x 20 Draft Diverter and Vent Connector: 6 Each Side to Nearest Wall: 6 Floor Opening (Length and Width): 32.31 x 20.31 Height: 23.5 Inlet to Floor: 18.38 Iron Pipe Size (N.P.T.): 0.5 Overall Length (Including Diverter): 40 Register Color: Tan Register Length and Width: 34 x 22 Size of Flue Collar: 4 Diameter Temperature Control Millivolt Wall Thermostat: Yes Two Adjoining Sides to Walls: 18 Type of Gas (State on Order): Natural or LP Venting Center of Flue to Floor Covering: 15.88 Venting Floor to Top of Diverter Shield: 9