... )Water-proof 4) Easy installation 5)Corrosion resistant The roof ventilation fan applies the theory of convection between natural wind and air ... ' health and enhances the working efficiency.It is widely used in warehouse, toilet, factory, workshop, stadium, tennis hall, assembly hall, garage ... : 390mmVentilation Diameter: 250mmBase Plate Dimension: 380mm*380mm Natural Power Turbo Ventilation Fan 250mm