ER16 collets are a fantastic toolholding system for small milling machines like the Taig, but keeping them organized is a pain. I needed a better storage system than the 'jumbled pile on a workbench' method that I had been using, and I've never seen any caddies or organizers for ER16 collets for sale.
I whipped up a simple box in SolidWorks to hold 15 collets with a matching lid. My original plan was to have hinges as part of the actual model, but I was in a hurry and just used the smallest hinges I could find at the home improvement store. However, hinges are entirely optional as the lid is keyed to the box with hemispherical bumps.