38 In.H-W Alu Universal Backdraft Dampr Frame Material Aluminum Number of Panels 1 Maximum Air Velocity 2250 fpm Overall Height 38 in Rough Opening Shape Square Fits Fan Diameter 36 in Free Area 7.3 sq ft Overall Width 38 in Frame Material Thickness 0.1 ga Frame Depth 1 5/8 in Rough Opening Length 36 in Maximum Pressure 1 in wc Rough Opening Width 36 in Blade Material Aluminum Single Acting/Double Acting Single Acting Closure Type Spring Flange Width 1 3/8 in