63 In.H-W 6 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 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