This is not just a marble machine. This is a marble machine that can handle an infinite cycle on four tracks at once! The body of the machine is a set of four intertwining tracks that are made for 3/8" ball bearings. In the middle sits a spiral, and on the top there is a lockcap, with a turncap sitting on top of that. When you put the marble bearing things on the track, they go to the bofrom, because gravity. But, when you turn the circle at the top (the turncap), it will make the spiral turn, moving the bearings back up to the top, where they can happily start the tracks again. The original model was designed my Tulip Laanen and the machine itself was happily printed at Do Space!!