I accidentally cut up one of my epoxy bottle caps, and decided to print a new one. It turned out great, threads up fine and everything! Designed so it doesn't need any supports (hence the slightly different geometry than the original on left) Inner Diam: 13/16" (20.6mm) Outer Diam: 15/16" (23.8mm) Thread pitch: 1/8" (3.2mm) Disclaimer: I haven't actually squeezed epoxy through this yet.