there is some controversy on how to colour the faces of this polyhedron. although the common way to fill in a polygon is to just colour its whole interior, this can result in some filled regions hanging as membranes over empty space. hence, the "neo filling" is sometimes used instead as a more accurate filling. in the neo filling, orientable polyhedra are filled traditionally, but non-orientable polyhedra have their faces filled with the modulo-2 method (only odd-density regions are filled in). in addition, overlapping regions of coplanar faces can cancel each other out. the difference between the fillings of this polyhedron is very slight, but still present.