A 24 mm wide 2x2x2 is needed to complete the puzzle. Buy Eastsheen Mini 2x2x2s at http://twistypuzzles.com/shop/index.php?main_page=product_info&cPath=1&products_id=7
for only $3.
This puzzle is 42 mm to an edge making it small enough to be affordable yet large enough to be truly enjoyed. It also has 24 additional hidden pieces to create a better quality puzzle. The concept was patented in 1985 by Sergey Makarov and Oskar Van Deventer produced his version (www.shapeways.com/model/31732/mixup_cube.html
) in 2009. Oskar Van Deventer supports the sale of this product.
This puzzle has 26 visible pieces as well as 24 hidden and the internal mini 2x2x2 (sold separately).
Difficulty Rating: 6