Appox 17.25 dia and 7 inch inside dia of pipe hole. Collar underside outside is 15 inches dia The is a beautiful Louvred Register Grate heating vent for a stove pipe. All original including patined Painted Surface.Please enlarge pics to view condition which is really nice w being dirty and old wear as shown. The item "Antique Cast Iron Stove Pipe Round Louvre Register Floor Vent Grate" is in sale since Thursday, March 15, 2018. This item is in the category "Antiques\Architectural & Garden\Hardware\Heating Grates & Vents". The seller is "amdew1" and is located in Essex, New York. This item can be shipped to United States.