45 In.H-W 5.75 In.L Alu Wall Exhaust Shutter, Damper Application Backdraft, For Nominal Duct Diameter Not Applicable, Frame Material Aluminum, Number of Panels 2, Maximum Air Velocity 2500 fpm, Overall Height 45 in, Rough Opening Diameter 42 1/2 in, Rough Opening Shape Square, Fits Fan Diameter 42 in, For Duct Shape Not Applicable, Free Area 10.3 sq ft, Overall Width 45 in, Frame Material Thickness 0.8 in, Overall Length 5 3/4 in, Connection Type Not Applicable, Frame Depth 3 in