These are very cool. They are somewhat smaller than I expected, and one set is certainly not enough. But they make light of teaching Pre-Algebra and in conjunction with some good Didax resources and a text book you'll be off and running. The picture does not point out that each tile is red on one side, so that when a number is negative it is "in the red", also if number needs to be moved to the "other side" of the equation, they can just be picked up and flipped over to the positive or negative equivalent. Smart.