4 india Galvanized Steel Fire Damper Damper Application Fire For Nominal Duct Diameter 4 in Frame Material Galvanized Steel Number of Panels 1 Maximum Air Velocity 2000 fpm Overall Height Not Applicable Rough Opening Diameter 4 in Rough Opening Shape Round Fits Fan Diameter Not Applicable For Duct Shape Round Free Area 0.1 sq ft Overall Width Not Applicable Frame Material Thickness 20 ga Overall Length 14 in Connection Type Not Applicable Frame Depth 14 in