Convolution Blockhead - A Stewart Coffin Wood Puzzle Brainteaser What an interesting and difficult puzzle designed by Stewart Coffin.  7 complex pieces will assemble sequentially to form a 4x4x4 cube. Really tests the spatial relationship skills. You will likely feel like a blockhead after working hours to solve this one.... Measures about 2 3/4" cube. Excellent fits on this puzzle make it challenging to even dis-assemble, but of course the real challenge is in the assembly. Level of Difficulty: Level 4