It is important to insulate dryboxes or other objects with installed PC4 fittings from air to keep dry environment inside.
This plug (spigot) can help you.
It seems better to print the plug using TPU (solid without infill), but I used PETG because it is a bit more elastic than PLA.
I printed 0.12mm layer height in order to keep diameter gradient more steady.
You can find fittings PC4 M10, on the AliExpress or on the Amazon
The author remixed this model.
Dimensions were changed to fit fittings.