4" to 2" Duct Reducer on a 92mm Case Fan Style Mount

This is an original design of a 4" to 2" duct reducer that allows mounting to a 92mm case fan or virtually anything if using fasteners such as wood screws or such. The 2" side will fit 2" PVC pipe. 

Photo #1 - 4" to 2" Reducer attached to a 2" pipe that was repurposed from a builtin vacuum 

Photo #2 - 4" to 2" plus 4" Duct Attachment ()