14 In.H-W 4.5 In.L Aluminum Backdraft Damper, Damper Application Backdraft, For Nominal Duct Diameter Not Applicable, Frame Material Galvanized Steel, Number of Panels 1, Maximum Air Velocity 2000 fpm, Overall Height 14 in, Rough Opening Diameter 12 1/2 in, Rough Opening Shape Square, Fits Fan Diameter 12 in, For Duct Shape Square, Free Area 0.7 sq ft, Overall Width 14 in, Frame Material Thickness 20 ga, Overall Length 4 1/2 in, Frame Depth 2 in, Rough Opening Length 11 1/2 in