These sets take marble runs to a whole new level and kids as well as adults will enjoy putting structures together and watching the small steel balls make their way through the creation. Basically, you have transparent interlocking cubes that you piece together. Some cubes simply have holes in them for the balls to fall through, some have slopes that allow balls to exit out either side of the cube, and some have slopes that allow balls to exit just one side of the cube. You can attach the cubes however you want, then see how the balls travel through the maze you've created! Cubes are color-tinted but transparent so you can watch the balls the entire time and they're made of polycarbonate so you know they're durable. The 50-Pack sets include 36 cubes and 14 balls while the 92-piece set includes 72 cubes and 20 balls. The open-ended creative fun with these sets will make them a treasure at your home. Please note that these sets have been re-released from MindWare and newer sets are not compatible with older sets from Q-Ba-Maze.