This is just a simple and very small bottle cap container, i.e. you use ordinary bottle caps as lid. It adds only 5mm height to most bottle caps. At least for all the caps I tried, the cap closed nicely and tightly.

EDIT: There are 2 versions (see second photo):

• high: for the older style caps with ca. 14mm height (PCO 1810)
• low: for the newer caps with ca. 11mm height (PCO 1881)

You might also be interested in a bigger, yet still small bottle cap container.

And I also made a wider version for some smoothie bottle caps.

Printing: I used PLA, 0.4mm nozzle, 0.2mm layer height.

Edit: added a rounded version, it's rounded inside and outside.