The Trax Expansion Set offers over 40 additional elements to extend your track. You'll keep the fun rolling when adding distance to your run and experimenting with height tiles, tracks and curves. Combine with the GraviTrax Starter Set and test your skills to see how long you can keep the marbles rolling. GraviTrax is a modular, electronic-free interactive track system where you can design and build your own marble runs. This STEM toy for boys and girls 8 and up, encourages experimenting with gravity, magnetism, and kinetics to propel your marble to the finish. Gender: unisex.