Three year olds can build a fantastic marble run with this colorful 20-piece set. Set the marbles on the spiral at the top and watch them roll from one level to the next, as the curved track gets steadily lower. Little bumps inside the track keep marbles moving steadily so they don't bounce out and a small cup at the end collect the marbles at the bottom of the run. As they're putting the marble run together, children are strengthening their reasoning skills and fine motor skills. Playing with the marble run encourages the development of creativity, problem solving and social skills, too. Made from ecofriendly PlanWood, with solid wood poles in graduated lengths. Suitable for children ages 3 and up. Sample pole length: 2.6 in x 2.6 in x 6.4 in.