I run a couple of filament spools above my printer on a tray and had some issues with filament jumping off the spool and become entangled in the the axle that the spool run on. Tried a couple of other guides, but designed this, with a PTFE lining to smooth out the running, and it seems to do the trick for me.

Printed in PLA and after printer slide a PTFE in the opening. It's got a stop at the bottom stopping the tube from falling out