11.5 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 11 1/2 in, Rough Opening Diameter 10 in, Rough Opening Shape Square, Fits Fan Diameter 10 in, For Duct Shape Square, Free Area 0.4 sq ft, Overall Width 11 1/2 in, Frame Material Thickness 20 ga, Overall Length 4 1/2 in, Frame Depth 2 in, Rough Opening Length 10 in