... :high resistant to corrosion,long life and high tensile,easy installation,no nosie,no energy cost. 1, curved blades is scientifically ... . 2, the central axis with fine steps, to make the turbine blades under high speed and never deformed, and thus greatly ... under in 0-22.5 ramp installation, the installation is very simple, generally within about 30 minutes can be installed. Roof turbine Ventilators