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A defining feature of this non-convex 20 sided polyhedron is that all of its dihedral angles are 90 degrees including the concave angles (blue edges) as well as the convex angles (brown edges).
It is also a “shaky polyhedron”. Useful in teaching geometry concepts.
Created by [David Hall](https://sketchfab.com/davidhall). This model has been used under a [Creative Commons Attribution license](https://creativecommons.org/licenses/by/4.0/legalcode).