axial fan hub,HUB of Axial Fans are made of Die-cast aluminum,so they are resistant to corros ion and high strength,in some cases,the number of blade assembled will be less than the maximun number of blades that can be installed.Columns such as 12 blades correspond to up to 12 blades in the Z-fan hub,but only 6 blades can be inserted,the remaining 6 blade root vacancies are inserted into a special insert.