20 in Backdraft Damper / Wall Shutter, 20-1/2 in x 20-1/2 in, DAYTON, Mfr# 4C559

23 In.H-W 5.75 In.L Aluminum Backdraft Damper, Damper Application Backdraft, For Nominal Duct Diameter Not Applicable, Frame Material Aluminum, Number of Panels 1, Maximum Air Velocity 2500 fpm, Overall Height 23 in, Rough Opening Diameter 20 1/2 in, Rough Opening Shape Square, Fits Fan Diameter 20 in, For Duct Shape Not Applicable, Free Area 2.3 sq ft, Overall Width 23 in, Frame Material Thickness 0.8 in, Overall Length 5 3/4 in, Connection Type Not Applicable, Frame Depth 2 1/2 in