A box packing puzzle invented by Leonard Gordon more than 25 years ago. This is the original version of the puzzle, made from joined spheres. The eight pieces are identical and sized so that they fit in a golf ball case. The sphere diameter is 13.8 mm.
It is possible to pack 6 of these pieces into the box in a way where it appears completely filled, with no room for any more pieces (or even one more sphere). This is an interesting way to present this puzzle to someone, can they add not one but two more pieces and close the box?
Golf ball case box on amazon.com