GraviTrax Loop $12.99 Default Title - $12.99 Quantity This product is coming soon. Please fill in the form below if you'd like to pre-order this item! Turn the marble upside down with the Loop accessory. Experiment with how much speed the marble needs to loop-the-loop. This accessory also includes 6 additional tracks. GraviTrax Starter-Set required. Recommended for children ages 8-99.