Summary I wanted to do something with snap together parts, and this idea somehow bubbled up. It turns out to be a wonderful fidget. Fidget wise, I prefer keeping the chain as a line instead of linking it into a circle. ALERT: For those that keep the chain as a line, I have provided a little end support because the open link on one end tends to get damaged. I experimented with the teeth on the pin part. At this size, each part length = 2.54 cm, the teeth design works nicely. None of my chains have come apart and that is with extensive fidgeting. When I scaled this up two times, the teeth were too rigid, and some of them broke off putting it together. So bottom line, if you are going to scale this, you may want to change the teeth design, and tolerances. PRO TIP: If you print out a set to give away, DO NOT put the chain together. Let them do it. :) Print Settings Supports: Yes Infill: 100% Notes: The small annular rings on the pin are angled so that they do not need support. Make sure that the supports only go inside the link with the two holes and the bridge. If you get support in the small groove of the pin, it can be difficult, but not impossible to remove.