GraviTrax Pro Extension - VerticalThe GraviTrax PRO Vertical Extension Set offers 33 additional elements to reach new heights with your track. Create dynamic marble runs with walls, pillars and balconies that take your tracks to new heights. Whether you create towering three dimensional structures or suspended tracks, see how high and clever you can build. Combine with the GraviTrax Pro Starter Set (sold separately) and take your track to a new level. This STEM system [Science,