This is a great puzzle for all sorts of situations, because it contains only three pieces. Incredibly, that's all that's needed to form a six-pointed cross, which is how the puzzle will arrive. Each of the wooden rectangles measures about 3 inches long and 2 inches wide. Two of the pieces resemble a capital C, and the third looks like an O ... and that's how the puzzle got its name. But it looks easier to put together than it actually is, so keep your wits about you as you take it apart for the first time.