26 In.H-W Aluminum Spring Backdraft Damper Frame Material Aluminum Number of Panels 1 Maximum Air Velocity 2000 fpm Overall Height 26 in Rough Opening Shape Square Fits Fan Diameter 24 in Free Area 3.6 sq ft Overall Width 26 in Frame Material Thickness 0.1 ga Frame Depth 1 5/8 in Rough Opening Length 24 in Maximum Pressure 1 in wc Rough Opening Width 24 in Blade Material Aluminum Single Acting/Double Acting Single Acting Closure Type Spring Flange Width 1 3/8 in