This adaptable and expandable ball track is a great introduction to the Kullerbu Play World with exciting elements for Paul the ball to pass through. Nothing can easily shake the Kullerbu tracks. The ramps, straight tracks, and curves each have holes into which the pins of the plastic connectors snap snugly into place. Kullerbu is the perfect combination of wood and plastic parts and highlights the advantages of each material making this sturdy play system from HABA one that will last for your child's entire childhood. 25 Piece Set Includes: windmill wheel ramp, large gateway, archway with bell, steep ball curve, a variety of track and 3 balls. Balls are 1 3/4" in diameter, ensuring safe play for children 2+.