This is a filament spool bearing. In fact, it is an adapter for fixing the one way clutch.
By attaching the bearing to the spool, the filament feeding is smoothed to prevent the step out, but if the rotation is too smooth, the spool may rotate in reverse due to the retraction of the filament during printing, and the filament may get caught. . To prevent this, use a one-way clutch to turn in only one direction.
The following parts are required to make this.
One-way clutch: HF0812 x 1
The initial version was only 57 mm in outer diameter. I added 52-57mm and 72-74mm.
This description is a machine translation of Japanese to English using Google Translate.