24 Cell Octaplex 4D Platonic Hypersolid 23mm

This is another projection of the '24 cell' which is the 6th regular convex form in four dimensions. 
Voted the favourite higher dimensional geometry by a survey of geometrers due to its many fascinating properties.
For instance, it is the only non-triangular form that is its own 'dual', meaning that becaise it has 24 vertexes and 24 octahedrons a smaller version can fit perfectly inside itself with one vertex touching the centre of each of the larger forms octahedrons. Also it can tile space without rotation but is not a cube.
More info about it can be found here https://en.wikipedia.org/wiki/24-cell
and you can also check out our own toroidal projection by searching for 'Metatron's Compass'.