These are compatible to the rhombic penrose tile set.http://www.shapeways.com/model/132549/penrose_tiles___13_skinny_rhombs___part_1_of_2.html?gid=...

You need 21 kites too to have a complete set.

Impossible triangle pendant. [Size: L] Also available in Small & Medium & and other (cheaper) materials! Wall-thickness: 3mm for all sizes. ...

The Penrose triangle, also known as the Penrose tribar, is an impossible object. It was first created by the Swedish artist Oscar Reutersvrd in 1...

These Cufflinks are designed to represent the Penrose Triangle (a.k.a. Impossible Triangle). Although being an impossible shape, this cufflinks a...