Prusa I3 spool holder arm

UPDATE 14/07/2015:

• Made de nut hole a bit tighter
• Added a lug on top of the frame holder.
  That's why there is now a right and a left version for each arm.

FIRST VERSION:

New shape and slightly less thickness to use less plastic.

Uses standard M4x20 screw with nut hole to tighten to the frame.

Versions for :

• 5, 6 and 8mm frame thickness
• 6 and 8 mm threaded shaft diameter.