63 In.H-W 6 1/4 In.L Alu Wall Backdraft Dampr, Damper Application Backdraft, For Nominal Duct Diameter Not Applicable, Frame Material Aluminum, Number of Panels 2, Maximum Air Velocity 2500 fpm, Overall Height 63 in, Rough Opening Diameter 60 1/2 in, Rough Opening Shape Square, Fits Fan Diameter 60 in, For Duct Shape Not Applicable, Free Area 20.4 sq ft, Overall Width 63 in, Frame Material Thickness 0.8 in, Overall Length 6 1/4 in, Connection Type Not Applicable, Frame Depth 3 in