This flex duct size and CFM chart covers all common sizes at two friction rates. The numbers are those you would obtain using a duct calculator, aka a ductulator. Pro tip:Remember to use a duct calculator for the kind of duct you are using. You might get incorrect results using a calc...
Fantech FKD16XL - FKD Series Round Inline Mixed Flow Centrifugal Fan, 16" Duct (4,274 CFM)- Fantech FKD direct drive, mixed flow centrifugal fans blend the high flow of axial fans with the higher pressure, non-overloading characteristics of backward curv