This DIY filament spool can easily be adjusted by different rod lengths or arm sizes. The current design is made for 8mm threaded rods between the center and the arms. You also need two 608 bearings for the center part. I tried around 3kg of filament on the big version with 13cm long threaded rods. Works just fine and helps to avoid tangled up filament.
We also offer the small version in our webshop: http://www.cubic-print.com/DIY-Filament-Spool