It comes with three large, 4.5 cm diameter marbles that rattle as they go intentionally slowly down the track, in order to prolong the magic and the surprise for your child. This run will stimulate children to experiment to find fresh solutions, to observe with interest the world around them, and to try out ideas through trial and error. This toy is designed to encourage your child's fine motor skills, creative thinking, hand-eye co-ordination and learning cause and effect. Suits ages 18 months +.