Take your marble run to the edge with the “GraviTrax PRO Extreme Starter-Set”! Test your creative limits and the laws of physics with the “GraviTrax PRO Extreme Starter-Set”! Vertical components and four action accessories from the PRO series (Splitter, Mixer, Turntable, Helix) combine to create more challenges, more possibilities, and more extreme fun! Set up’s a snap as children explore STEM concepts while engaging in independent, creative play. Simply add more accessories for endless possibilities to experience the power of gravity and educational fun today!