A truly mesmerizing marble-track experience! Each set is made up of hollow stacking cubes and a variety of perfectly flat tracks. The paths cut out of each track widen almost imperceptibly from one end to the other, creating an invisible slope that propels the marbles forward. Watching them go is like magic in slow-mo! For Ages 8 and up. WARNING: CHOKING HAZARD - Small Parts. Not for children under 3yrs. CHOKING HAZARD -- Toy contains a marble. Not for children under 3 yrs.