This spool fits the Rostock Max and holds a kg of filament.
Also see http://www.thingiverse.com/thing:116104 for a one piece custom spool.
This is a customized version of http://www.thingiverse.com/thing:45101
I put the two parts of the spool in separate files because they both won't fit on the Rostock bed at the same time. Print with 100% infill.