13.8 In.H 11.8 In.W 3.7 In.L GStl Sprng Fire Dmpr, Damper Application Fire, Frame Material Galvanized Steel, Number of Panels 1, Maximum Air Velocity None, Overall Height 11 3/4 in, Rough Opening Diameter Not Applicable, Rough Opening Shape Rectangular, Fits Fan Diameter Not Applicable, For Duct Shape Rectangular, Free Area 0.8 sq ft, Overall Width 13 3/4 in, Frame Material Thickness 22 ga, Overall Length 3 3/4 in, Connection Type Not Applicable, Frame Depth 3 3/4 in