35 7/8 In.H-W Aluminum Ceiling Truss Damper, Frame Material Aluminum, Number of Panels 1, Maximum Air Velocity 1500 fpm, Overall Height 30 3/4 in, Rough Opening Shape Rectangular, Fits Fan Diameter 30 in, Free Area 5.4 sq ft, Overall Width 35 7/8 in, Frame Material Thickness 0.1 in, Frame Depth 1 5/8 in, Rough Opening Length 28 3/4 in, Maximum Pressure 1 in wc, Rough Opening Width 33.9 in, Blade Material Aluminum, Closure Type Gravity, Flange Width 1 5/8 in