This deceptively simple shape forms complex 3D patterns. Put a bowl of these on your coffee table for your friends to ponder!

It takes a while to figure out the range of ways that this shape can fit together. The pictures above show samples of some of the building "units" of 3-4 basic shapes that can be combined to form flat or 3D structures.

The end faces of the two joined tubes are congruent to the faces of the tetrahedrons and octahedrons in an isotropic vector matrix. The faces of the short tubes are congruent with the octahedron faces, while the longer tubes are congruent with the faces of the tetrahedron.

The "Double Whole" file is provided for reference only and is not intended to be printed.

The "Octa" and "Tetra" sides of the shape are printed separately and glued together. The sides must be perfectly aligned in order for multiple shapes to fit together properly. The "flat" pieces leave it to you to get accurate alignment, the "connector" pieces let you use two copies of the "Double Tube Connector" to ensure proper alignment.

The holes accept 3mm x 3mm cylindrical magnets. It is a good to clean the holes out with a 1/8" drill bit to remove and burrs or imperfections prior to inserting the magnets. Polarity of the magnets should be opposite for the "tetra" and "octa" ends of the tubes. Secure magnets with a dab of CA glue.