Rubiks Cube 5x5: Like no other cube before, the 5" x 5" is a must-have for the true Rubik's aficionado! Rubik's Professor Cube® is the most complex of all Rubik's Cube levels. Its siblings and predecessors bow down to the challenge this one introduces to the user. Newly tooled and released, this is a long awaited puzzle for Rubik's fans looking for a piece of nostalgia and those who have just learned how fun Rubik's products can be.