... screw ,It will never broken andblow off the hub4,GeneratorOulu generator is made of SUS304 material .It will not rustThe magnets ... full Intelligent controller,Voltage rise,auto brake,autounloading,12/24V auto distinguish,auto week up and so on ,It will protectthe generator ... energy!ENGINEERING APPLICATION CASEFinishing workshopCustomer visit our factory 400w windturbine generator