Shutter Mount Exhaust Fan, Assembled Assembled, Blade Diameter 18 in, Blade Material Aluminum, Control Type Wired into Electrical System, Drive Type Direct Drive, Duct Diameter Not Applicable, Exhaust Airflow @ 0.000 in SP 3,000 cfm, For -Out Height 20 3/4 in, For -Out Width 20 3/4 in, For Maximum Wall Thickness 5 1/2 in, For Minimum Wall Thickness 3 1/4 in, Frame Finish Galvanized Steel, Frame Material Aluminum, Guard Finish Powder Coated, Guard Material Steel, Guard Type Exhaust