Wind-Driven Turbine Exhaust Ventilator Bracing Location External Head Diameter 25 1/2 in Throat Diameter 16 in Airflow @ 4 mph 950 cfm Metal Material Thickness 22 ga 24 ga Overall Height 21 3/4 in Overall Width 25 1/2 in Housing Material Steel Bearing Type Lower Thrust Ball Bearing Oilless Bronze Upper Bearing Bracing Material Steel Housing Finish Galvanized Includes - Installation Requirements Base for New Installations Flashing