12" x 12" Mill Flush Type Louver, 15" x 15" Overall Size, Ventilates 117 SQFT, Heavy Duty Aluminum Construction, 1-1/2" Wide Mounting Flange, 8" x 8" Attached Screen For Insect Protection, Built In Weather Protection, Used For Exhaust Attic Ventilation, Must Be Accompanied By Intake Vents.