Gravity Ventilator, Low Profile, Fan Size: 36", Fan (Not Included), Damper Size: 37" X 37", Base Dims: 40 1/2" X 40 1/2", 4191/466 CFM/Throat Velocity @ 0.050-In Sp Gravity Intake, 7251/806 CFM/Throat Velocity @ 0.100-In Sp Gravity Relief, 6626/736 CFM/Throat Velocity @ 0.125-In. Sp Gravity Intake, 8381/931 CFM/Throat Velocity @ 0.200-In. Sp Gravity Intake, 9371/1041 CFM/Throat Velocity @ 0.250-In. Sp Gravity Intake, Max Intake CFM/Throat Velocity 11634/1225, Construction Material: Galvanized Steel, Designed For Applications That Require Nonpowered Ventilation or Can Be Used In Conjunction with Powered Exhaust, Supply, or Reversible Fans, Weathertight Hood Is Constructed Of Interlocking, Arched, Galvanized Steel Panels, Bird Screen And Hood Come Preassembled, Base Requires Field Assembly With Included Hardware, Dims Of Weather Hood: 15" H X 53" W X 59-1/2" D, Overall Dims: 38"H X 68"W X 60"D, Weight: 300 Lbs, In Bulk, Made In USA