... , 3.easy to operate Roof ventilator Character: 1. Zinc of steel:180g/m2, stong rust resistant capability, long severce life ... angle turbineturbine can be altered, This kind of turbine can be installed on many kind of roof , easy to operate. 3. ... bearing,(2)this kind of complete insulating motivates system can ensure ventilator work more smoothly and efficiently. automatic wind driven roof ventilator