The Air Louvers VLFR-B is a Standard Round Shape Vision Kit, that is 1" Visible, is For use with 1 3/4" Thick Doors, is 18 Gauge, Accepts 3/16"-1/4" Thick Glass, is constructed of CRS (Cold Rolled Steel) is available in 12", 18" and 24" Diameter, and comes in a Mineral Bronze finish.