GraviTrax Magnetic Cannon $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! Boost your speed using magnetic force! Launch the marble through your run by adding the Cannon. The high-powered magnet gives the marble speed to help extend your run by boosting it up inclines and down tracks. This accessory also includes 3 additional marbles. GraviTrax Starter-Set required. Recommended for children ages 8-99.