The tracks are made of foam pipe insulation, which I ordered from Amazon here. On this day we were making bumper coasters. The kids would release a marble at the highest point, it would hit another marble on the track, and the goal was that they marbles would NOT go into the cup. They learned a lot with this hands-on activity about potential and kinetic energy.
The activity came from mysteryscience.com. If you are not familiar with this site click right over to check it out!