This Xyloba building kit is designed as an extension to all sets. It contains additional rails and connectors for increasingly complex structures and longer melodies.  And with the two "mute tone plates", new rhythms with pauses can be built.. 

Contents:
1 long rail, 2 short rails, 2 building elements, 1 building element with a passage for long rails, 2 building elements for notes, 2 mute tone plates

Visit Xyloba's home site in Switzerland for additional images and information.  Ages 3 and up.  CAUTION:  Marbles can represent a choking hazard to very young children.