Ball Bearing Link Fidget toy.

thingiverse

This was designed for 3/4 inch (19mm bearings) but with some simple math it can be scaled to just about any bearing size. I even made a little necklace with 6mm Airsoft BBs with this. (Scale to 31% for 6mm). Instructions: 1. Download and print at least four links. - Pick the wishbone style (BearingLinks07.stl) or the normal style (BearingLinks08.stl) or mix them up. 2. Get some 3/4 inch (19mm) bearings. (Or scale to the size of bearings you have.) 3. Pop the bearings into the links and assemble into a square. 4. Optional - Add more links and bearings if you want. Some common scales: 31% for 6mm bearings/Airsoft BBs 83% for 5/8th inch or 15.85mm bearings Where Scale = 100 * (Measure size of your bearing / 19 mm) *Warning 1: Please do not swing this around - the bearings can be heavy and fly off of the links and hurt someone or something. **Warning 2: Due to the small parts being a choking hazard, do not use this around babies or toddlers.