Trestle Tracks consists of hollow stacking cubes and perfectly flat tracks with cutout paths that widen almost imperceptibly to propel the marbles forward. Watching them go is like magic in slow-mo! And with the Pro set, you don't just get an overabundance of cubes and tracks. You also get a variety of totally new trick tracks that catch, release, bounce, combine, swoop, and more. Marble-run fun reaches new heights of wonder with Trestle Tracks Pro! WARNING: Choking hazard! Not for children under 3 years of age.