This is one of my favourite puzzles and certainly one I get asked about a lot. To make it I extended some of the normally hidden interior parts of a 4x4x4 Eastsheen Cube to the surface. As with my Ball in a Cube puzzle it has a central block which hinders certain movement. It is difficult to understand the effect of this block on the puzzle without handling it. Many people believe the block stops the puzzle being fully functional. However this is far from true since the block has always existed in the mechanism and does not prevent the full mixing of the puzzle. Removing the block would add functionality though would be a completely pointless exercise since the block is what makes it and my Ball in a Cube unique solving challenges. It's a bit like saying a Skewb is not fully functional since the corners can't turn. Without the block you just have a regular 5x5x5 with a few parts missing. In addition the middle row would be awkward to move and line up. The block makes it a difficult and unusual puzzle to solve.
I am very pleased with the quality and rotational movement is smooth. I used regular Rubik's Cube style stickers for this puzzle.
See- http://tonyfisherpuzzles.net for photos and more information.