... 2. Imported bearing, high-strength, low noise, durable;3. Using air downstream principle, pvc shutter or aluminum shutter, antioxidant, light weight ... , no distortion, open and close sweetly, prevent backflow of air; 4. High-strength more high-gluten strength aluminum-magnesium alloy ... CCC certification. Also protection class:IP55, insulation class: F grade. air cooling system for poultry house