OK, like the Hongdian nib holder https://www.thingiverse.com/thing:6626432 this is one for Jinhao nib units.

The three sizes I have are #8, #6, and #5. Like the Hongdian variant, the #5/#6 is a single container, and the #8 is a separate conatiner.

I printed these with PLA using a 0.4mm nozzle and 0.08 layer height, no supports. The threads on the #5 nib unit are 0.7mm pitch, so I think you need a very thing layer height to be successful with these threads.

One other new addition, I added inset text on the bottom J (for Jinhao) and either 8 or 5/6 to denote size. Somewhat helpful so you don't have to open each case to find the one you want (at least brand).