I have been using this http://www.thingiverse.com/thing:45930 spool holder and happy so far. However, I need the spool to be on top. After some searching could not find a suitable one so design this. This is a spool holder arm designed to sit on top of Prusa top parallel bars and using the same spool support from http://www.thingiverse.com/thing:45930. I intend to make this beefy, 7mm thick to hold 1-2 kg of spool; and some holes to save material and look nicer. This works with regular filament spool of 18-20 cm diameter and 8cm height. The scad file is included so you can adjust yours when necessary. Enjoy! Print 2x of the STL as provided (horizontal) with support. The support is required for the bar slots since printing this horizontal makes the top part above the slot overhang. Slot the arm onto the top bars vertically then you can attach the spool. I am using the original spool support from http://www.thingiverse.com/thing:45930 to keep the spool.