Manual Damper, Damper Application Backdraft, For Nominal Duct Diameter Not Applicable, Frame Material Fiberglass, Maximum Air Velocity Not Rated, Overall Height 27 1/8 in, Rough Opening Diameter Not Applicable, Rough Opening Shape Square, Fits Fan Diameter 24 in, For Duct Shape Not Applicable, Free Area Not Applicable, Overall Width 27 1/8 in, Frame Material Thickness 2.6 mm, Overall Length Not Applicable, Connection Type Not Applicable, Frame Depth 3 3/8 in, Rough Opening Length Not Applicable