57 In.H-W 5 1/4 In.L Aluminum Backdraft Damper Damper Application Backdraft For Nominal Duct Diameter Not Applicable Frame Material Aluminum Number of Panels 2 Maximum Air Velocity 2500 fpm Overall Height 57 in Rough Opening Diameter 54 1/2 in Rough Opening Shape Square Fits Fan Diameter 54 in For Duct Shape Not Applicable Free Area 17 sq ft Overall Width 57 in Frame Material Thickness 0.8 in Overall Length 5 1/4 in Connection Type Not Applicable Frame Depth 3 in