This is a little container for....whatever YOU decide to put in it. Interior diameter is 16mm. The cap and base have a gap of 0.1mm modeled between them. I chose this gap with the idea that I'd print the part with a 0.3mm layer height and probably get a snug "just right" fit because of the striations of the layers. Turns out, I was right. The cap fits snugly, and you can hear/feel the layers of the cap and base interlocking as it goes on. It won't come open in your pocket and you can pry it open using a fingernail or two.
Thickest part of the wall on the base is 3mm. Interlocking wall thicknesses are 1.5mm. Top and bottom are modeled 1.5mm thick. The example I printed in the pic is "transparent" PETG. Very straightforward one shot kill. You don't need to do anything special to make this work, but bear in mind that it was designed for PETG and the fit may not be as good with filaments that have different amounts of shrink.
2d circle sketches extruded into 3d. Pure rocket surgery.