1. Suitable for large-scale chicken farm as effectively ventilation equipment to reduce the tempreture and prevent diseases inside the chicken coop. 2. It can be directly installed in the side wall. 3. Made of excellent quality engineering plastic by injection molding for higher density and firmness. 4. UV resistant raw material is added for stronger anti-aging ability, longer service life, better sealing and flexible open, with anti-bird net. 5. Double row springs guarantees better sealing.