Anti-puncture system for the rear wheel of the bike. Anti-puncture system dedicated to all motocross riders who want to tackle any track without the uncertainty of not completing their race or simply not having the inconvenience of a puncture during a training, also guaranteeing the same performance normally offered by an inner tube. Thanks to its high elasticity, it adapts to any type of tire, managing to 100% fill the casing. The cross mousse reaches the highest levels of elasticity after only a few minutes of use, while at rest it resumes its initial hardness. At the end of use, it is advisable to leave the motorcycle at rest for a few minutes on a central trestle, to allow the mousse to resume the initial shape and hardness. The mousse is intended exclusively for off-road use, therefore it is not approved for public roads. Specifically designed for motocross. Optimal pressures even in extreme conditions. High elasticity.