The Fun Block puzzle is a six sided block with five axes of rotation, originating at three different points. One axis at the center of the puzzle allows pieces from the two halves to exchange sides, and the four peripheral axes allow 90 degree turns. This lets the orbiting pieces change orientation, which leads to the shape-shifting capability of Fun Block.
Fun Block comes as a DIY kit of parts, and you will need to supply your own stickers. The templates for the stickers are available in the instructions forum.
I recommend that you purchase the puzzle in "Black Strong & Flexible". It costs a bit more than the white material, but it's worth it since the finished puzzle will look and work better. All of the parts snap together, so no additional screws, springs, or other hardware are required. With Fun Block you can't make a mistake with the assembly. Since the parts can be assembled onto the core even after the core halves are snapped together, you can assemble the puzzle in any order you desire.