A small pill box intended for a keychain or similar. It has a twist lock that closes and opens with a nice click, and it doesn't open by itself.

The first click time closing might take a bit more force to get everything in shape, but the lock notch is a bit springy and closes quite reliably.

Sizes are inside diameter x inside height  ("3" is actually 3.4mm and “6” is actually 6.5mm)

If you need other sizes, you can ask in the comments and there's a good chance I'll upload it.

Printing: 

0.4mm nozzle, 0.15mm layer height (0.2 should also work),

octagon spiral bottom infill, concentric top infill (for decorative effect).