45 In.H-W 5.75 In.L Alu Wall Vent Shutter Damper Application Backdraft For Nominal Duct Diameter Not Applicable Frame Material Galvanized Steel 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 20 ga Overall Length 5 3/4 in Connection Type Not Applicable Frame Depth 2 1/2 in