I really like pjvpjv's spool rollers for the 2020, but with the spool off to the side, I still have issues with filament sliding off the side of very full spools, then winding around the 2020 support rail and getting stuck. Hence this filament guide, which guides the filament off the spool from the center.
I printed it in ABS and smoothed the inside with a bit of acetone, though that's probably not necessary. Works like a charm.
You need two 30mm M3 bolts to bolt it into the stepper motor. The existing bolts won't be long enough.