

This cube is formed out of four kaleidocycles (a chain consists of 16 tetrahedral links).
Two of them form octahedra. Two of the kaleidocycles form tetrahedra. The tetrahedra have the size of the cubeinscribed The volume of the two cubeinscribed tetrahedra plus the volume of the two cubedual octahedra are the same as the volume from the surrounding cube. You can buy also the cube forming elements (tetrahedron and octahedron) separate. 

