Rubik's 5 x 5 Cube
The Rubik’s 5" x 5" cube is the ultimate Rubik’s challenge. With almost twice as many cubes as the original, the Rubik’s 5 x 5 claims to have 283 trevigintillion different permutations. (That’s a lot of “illions”). No solving instructions are included, but they can be found on the Rubik’s Cube webpage when you reach the end of your rope, er, cube.