Sunforce Air X Marine Wind Turbine Acid etched castings double coated with marine grade powder coat for superior protection from the environment Tuff-Gel coated fasteners to prevent seizing of components The turbine&#8217;s smart controller allows it to actually control blade rotation speed thus eliminating the buzzing noise commonly found with most small wind turbines. High Wind Safe Mode - automatically slows turbine in potentially damaging winds. Reduces noise and distractions for peace-of-mind when on or off your boat Auto-brake feature that slows the AIR to a silent spin when the batteries are charged, thus extending bearing life and eliminating noise