... -cone fans) 1. Reasonable cone designing, low noise, big air flow, strong ventilation, low operating cost;2. Imported bearing, high- ... strength, low noise, durable3. Using air downstream principle, pvc shutter or aluminum shutter, antioxidant, light ... no distortion, open and close sweetly, prevent backflow of air,4. High-strength more high-gluten strength aluminum-magnesium ...