Cast Iron Round Floor, Ceiling, or Wall Grates for Air or Heat Vent. Register Cover Without Damper, 12" Boot Size, 14" Overall Diameter (ZM-IR-1202)

ZM-IR-1202  Round Cast Iron Grille 12" Hole Size Without Damper; 14" Exterior Diameter

Made to fit into a 12" round hole or duct, these grates have an exterior diameter of approximately 1" greater than their boot size. The flange measures 3/16", and is pictured in the side view photo. You may need to modify for different mounting applications.

None better anywhere at any price.