36 In.H-W Aluminum Ceiling Truss Damper, Frame Material Aluminum, Number of Panels 1, Maximum Air Velocity 1500 fpm, Overall Height 37 3/4 in, Rough Opening Shape Rectangular, Fits Fan Diameter 36 in, Free Area 7.1 sq ft, Overall Width 36 in, Frame Material Thickness 0.1 in, Frame Depth 1 3/8 in, Rough Opening Length 35 3/4 in, Maximum Pressure 1 in wc, Rough Opening Width 34 in, Blade Material Aluminum, Closure Type Gravity, Flange Width 1 5/8 in