I made and evaluated several hubs.

Type-A: One side is a ball bearing and the other is a friction bearing. It turns lightly, but the filament does not loosen. It is good performance.

The M6 screw rod was used for the shaft.

The ball bearing is made of polyacetal and has an outer diameter of 26 mm, an inner diameter of 6 mm and a thickness of 7 mm.

Type-B: The M8 screw rod was used for the shaft. It was attached to JGAURORA A3.

The hub is turning directly on the M8 threaded rod. Concerned about wear.

Both types A and B conform to the following spools. Polymakr Black Spool 55.2ｍｍ 　( 54.4mm ) eSUN Black Spool 53.5ｍｍ 　( 52.8mm ) eSUN Clear Spool 51.60mm 　 ( 51.0mm )