30-40mm Adapter
thingiverse
Just swap in that existing screw from your 30x30x10 fan, and the 40mm fan will slide right into place in the adapter. The adapter comes with a matching hexagonal grill, so just clip it onto the fan. Be sure to flip the grill on the slicer when you're done.
Download Model from thingiverse
With this file you will be able to print 30-40mm Adapter with your 3D printer. Click on the button and save the file on your computer to work, edit or customize your design. You can also find more 3D designs for printers on 30-40mm Adapter.