33 In.H-W 13.3 In.L Squ Stl Mtrzd Cntrl Dampr For Nominal Duct Diameter Not Applicable Damper Application Motorized Number of Panels 1 Overall Height 33 in Overall Length 13 1/4 in Rough Opening Shape Square For Duct Shape Square Overall Width 33 in Frame Material Thickness 14 ga Blade Material Galvanized Steel Maximum Air Pressure 4 in wg Overall Diameter 33 in Rough Opening Length 31 in Rough Opening Width 31 in Damper Type Dynamic Maximum Air Velocity 3500 fpm