... 3.imported bearing,mitsubishi belt 4.siemens motor optional Parameter for 50inch Butterfly cone exhaust fan: Model specification Blade/m ... 2. Imported bearing, high-strength, low noise, durable;3. Using air downstream principle, pvc shutter or aluminum shutter, antioxidant, light weight ... CCC certification. Also protection class:IP55, insulation class: F grade. air cooling system for poultry house