Skyrail Suspension is the only marble run in the world that reproduces the spectacular technology of suspension bridges. -- First you construct a central tower over three feet tall. Surround it by an arial marble track suspended by ajustable cables. With 12 yards of track you can construct marble run where marbles don't just travel downward at a constant speed. They can accelerate down steep slopes then climb uphill until almost coming to a complete stop, then roll quietly along flat plateaus, then plunge once again down chilling slopes at full speed. -- Marble sizes of 14mm to 21mm can run along the tracks. Marbles can be of any material and any weight. Includes detailed users guide with suggestions for activities. -- Great for educational purposes, as well. Design and conduct experiments that demonstrate speed, acceleration, gravity, centrifugal force, kinetic energy, inertia, friction and other essentials of physics.