61.75 In.H-W 4.5 In.L Aluminum Backdraft Dampr Damper Application Backdraft For Nominal Duct Diameter 62 in Frame Material Galvanized Steel Number of Panels 2 Maximum Air Velocity 2000 fpm Overall Height 61 3/4 in Rough Opening Diameter 62 in Rough Opening Shape Square Fits Fan Diameter 60 in For Duct Shape Square Free Area 27 sq ft Overall Width 61 3/4 in Frame Material Thickness 20 ga Overall Length 4 1/2 in Frame Depth 2 in Rough Opening Length 62 in Maximum Pressure 1 in wc