Gyrochoron

A gyrochoron, also known as a step tegum, is an isochoric polychoron formed as the dual to the step prism. It can have any number of cells as long as it is more than or equal to 5, while still remaining isochoric. The cell of a gyrochoron always contains two-fold rotational symmetry, and all of its faces contain mirror symmetry. The only possible vertex figures for gyrochora are trapezohedra, tetragonal disphenoids, rhombic disphenoids, and phyllic disphenoids, which are related to the possible cell types of step prisms.

Like the dual step prisms, some gyrochora can be swirlchora based on dihedra.