I was having a play on Autodesk Fusion as I'm trying to teach myself 3D drawing, so I can design things for my 3D printer, and I came up with this ball and socket which I thought would make a good fidget toy.

It is fairly loose as I designed it so it could be put together easily and not be too hard to move.

But it is definitely good fun to spin around and hold the socket while moving the ball into each 90 degree slot.

I'm sure the kids will think it's fascinating and it would be fairly educational as well considering we have some of them in our bodies :)