Vòng bi dùng bi Airsoft 6mm

Ball bearing with 6x 6mm airsoft plastic BBs. 

The 6mm BBs are super inexpensive at like 10$ for 3000pcs - would recommend quality BBs from G&G or BLS at 0.30gram or heavier, they're generally of higher quality than lighter ones that may have seams making them less than ideal for this.

Diameter 27mm, width 11mm. Center hole is 5mm.

I used 0.15mm layer height and 0.4mm nozzle. I wouldn't expect them to print well with a larger nozzle or thicker layers, at least not the cage.
No specific settings are required, I tried various settings as well as 100% and 0% infill.

Check if BBs can move freely through the holes of the cage before assembling, if not use scissors or other deburring tool.

A few drops of silicone oil or Super Lube #21030 works well for lubrication.

After assembling stick a screwdriver through the center hole and run the bearing back and forth on a mouse pad or similar surface while applying some pressure to wear it in.