... installation 5)Corrosion resistant The roof ventilation fan applies the theory of convection between natural wind and air to accelerate ... are exhausted effectively. It also can effectively remove indoor soot, smoke, odor, moisture, heat, decorative harmful gas, dust, human ... Diameter: 390mmVentilation Diameter: 250mmBase Plate Dimension: 380mm*380mm Natural Power Turbo Ventilation Fan 250mm