... .strong ventilation,big airflow 2.high quality galvanized sheet 3.imported bearing,mitsubishi ... bearing, high-strength, low noise, durable;3. Using air downstream principle, pvc shutter or aluminum shutter, antioxidant, ... , open and close sweetly, prevent backflow of air; 4. High-strength more high-gluten strength aluminum ... class:IP55, insulation class: F grade. air cooling system for poultry house