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 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.