Small 15-4 double step prism

The small 15-4 double step prism is a convex isogonal polychoron that consists of 15 rhombic disphenoids, 90 phyllic disphenoids of three kinds, and 60 irregular tetrahedra. 2 rhombic disphenoids, 12 phyllic disphenoids, and 8 irregular tetrahedra join at each vertex. It can be obtained as the convex hull of two orthogonal 15-4 step prisms.

This polychoron cannot be optimized using the ratio method, because the solution would yield a medial 15-4 double step prism instead.