... are widely used in agriculture and industrys ventilationcooling system and heating system.Application for: animal husbandry, poultry house, ... ,Imported bearingUsing air downstream principle, pvc shutter or aluminum shutter,antioxidant, light weight, no distortion,open and ... prevent backflow of airHigh-strength more high-gluten strength aluminum-magnesium alloy wheel, light weight, high strength, ...