This is a Mechanism that transforms a Tetrahedron into an octahedron. It's not really a fidget, just interesting.

You need

4 Triangle 1
4 Triangle 2
12 bridges
28 Connectors
The tool is optional-

There are also "All" Files that have everything you need for a full assembly on one plate.

Print Settings

Standard no Supports.

Assembly

I made an Assembly Video you can find here Watch the video.
There is also a PDF Assembly guide included inside the download.

Happy printing.