This is an adapter to be able to attach the Filler rolling spool holder to the stock filament holder mount that is provided with the Ender 2 Pro.
Just print this adapter and then the following files from here:
3DPNFilHoldRoller.stl
3DPNFilHoldGuide.stl
https://www.printables.com/model/174620-filler-filament-holder
The author remixed this model.