Spool roller with ball bearings for smooth rolling.

The sides are drawn in such a matter that they are a mirror it's only one part. Just put the bearings in and screw them together.

There are optional bars to slide them apart or you can print dampers in TPU to prevent them sliding around.

Hardware used:

4x ball bearing 608zz

4x Machine screw M3x14

4x M3 hex nut