Strong Spool Holder for Prusa i3 Single Frame

This is a quick rewrite of the http://www.thingiverse.com/thing:196070, using two M8 threaded rods.

It is perfect for me, it is on the upper side of the prusa frame, and I can use the rod to keep the PTFE tube close to the printer.

You need 4 608 bearings, 8 wahsers, 8 nuts M8, and two small rods m8 threaded.