A tiny threaded bottle cap, to replace the one for my red food coloring, that I flung into a bush when a bee went after me. (Long story.) Screws onto plastic Market Pantry assorted food coloring bottles that I bought at Safeway. An egregious waste of time and brainpower? Yes indeedy! Chamfers all over the place! Non-threaded area, deep inside, keeps liquid in.

Outside diameter: 16mm Thread pitch: 2.2mm Inner diameter of lid without threads: 13.9mm Outer diameter of bottle without threads: 11mm

You can open in customizer; all dimensions are in millimeters; some dimensions are not customizable, which might screw up the cap (uh, yeah). Written in OpenSCAD. Uses Yet another thread library for OpenSCAD – quickthread.scad:

• https://www.thingiverse.com/thing:2277141/files

Printer: My FFD printer (HE3D K200 delta) made a very crude approximation, with an interior full of random filament strands. My resin printer (Sonic Mighty 4K) made a crisp, clean, functional part, that screws on nicely. Although 3D printed stuff is generally not food safe, I think resin-printed things lack the crevices for bacteria and mold.