1.Stainless steel blades:big air volume, no deformation, no breaking and elegant appearance and durability. 2.Belt automatic tightening facility to ensure the belt will not loose or drop. 3.Calibrated by advanced computer dynamic balance tester, to achieve smooth operation, reduce noise, enhance stability, and extend service life. 4.Swung drop hammers: high quality nylon material ensure the shutters open and close flexibility. Galvanized Steel frame,SS blade Widely used in poultry farm,greenhouse,supermarket,textile mills,garment factory,inductry workshop and other sited need cooling and ventilation.