Wind-Driven Turbine Exhaust Ventilator, Bracing Location External, Head Diameter 16 1/4 in, Throat Diameter 10 in, Airflow @ 4 mph 425 cfm, Metal Material Thickness 24 ga, 26 ga, Overall Height 16 1/4 in, Overall Width 16 1/4 in, Housing Material Steel, Bearing Type Lower Thrust Ball Bearing, Oilless Bronze Upper Bearing, Bracing Material Aluminum, Housing Finish Galvanized, Includes -, Installation Requirements Base for New Installations, Flashing