With the GraviTrax PRO Element Helix, up to six tracks can cross each other. How many balls can pass through the helix in one go? With the GraviTrax PRO Element Helix, up to six tracks can cross each other. When a ball rolls into the helix, it leaves the PRO Element at a lower level. This means that up to six balls can travel along the stone at the same time. Combined with any GraviTrax starter set, the PRO Element Helix gives the ball track a whole new impetus and energy. GraviTrax is a flexibly expandable, interactive marble run system for children aged 8 and over: With GraviTrax, children, teenagers and adults don't just build simple marble runs. They create unique marble run worlds. By freely designing the marble runs and exploring the rolling behaviour of the marbles, the understanding of science is sharpened and gravity can be experienced at first hand. The GraviTrax universe includes three exciting lines - CORE, PRO and POWER. All GraviTrax lines and products can be freely combined with each other. The GraviTrax universe can be expanded infinitely with countless extensions with classic building elements or bricks that enable special action and tricks. So everyone can tinker, try things out and build beyond themselves.