What makes this unique is that it requires only four parts to build a 2x2x1 Rubik's style puzzle. No screws, pins, or caps necessary! Assembly requires a little ingenuity, but the Strong & Flexible material allows it to snap together. Don't try to disassemble it.
UPDATE: Version 3 corrects a cosmetic flaw that left visible gaps between the hollow pieces.
Video at http://www.youtube.com/watch?v=6D8cgcwJ_Bc