ZM-IR-602  Round Cast Iron Grille 6" Hole Size Without Damper; 7 1/2" Exterior Diameter
	Made to fit into a 6" 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.