Simplistic spool that takes advantage of the cardboard core on matter hackers refill spools. 

printed mine in PLA and PETG

200mm Diameter outside

80mm core hub

Made for 5/16" standard hex bolt, right in the middle keeping the core of the refill rolls as the new spool center. 

only works on rollers, but that's the best was to dispense filament anyway, IMO

designed solid and uses custom infill settings to expose infill on the outer part but still fill the top and bottom of the core for strength. 

you can import the .3mf file as a project in PrusaSlicer to have these settings

my favorite roller system is part of the prusa mini kit:

https://www.printables.com/model/57214-mini-printable-parts