Fixed couplers 4mm/8mm

Just a simple fixed-style couplers for 4mm motor shaft -> 8mm threaded rods.
I made this to test if was better to use a non-flexible design vs the classic alluminum flexible ones.
For me, this works better and reduce the wobble effect (coupled with this anti-wobble:http://www.thingiverse.com/thing:1638253)

Hardware needed:
4x M3 Nuts
4x M3x16mm screws or M3x20mm

Print the parts in vertical position, just like in the photo!