Summary

This design is used to increase the diameter of the Prusa MK3 i3 spool arm to allow larger diameter filament rolls to fit on the stock spool holder without hitting the metal frame. This mod can be easily added by twisting off one arm of the spool holder.

i.e. the MakerBot filament rolls are very skinny and have very larger outer diameters. The spool was hitting the metal frame of the printer and getting stuck. This lifted it up enough to allow it spin freely.