IFMAR legal, specially-designed 4WD front wheels with 12mm interior hex. Perfect fit, and perfect for high-competition race. The tires are manufactured from flexible product while still being durable against impacts. The side of wheel is aerodynamic for optimum performance. Medium hardness. Special options that come with the wheel are visible from the inside: reinforcement ribs to make the wheels as stable that you can and eradicate deformation. Set of 5 pairs (10 pcs) the price of 4 pairs. A fantastic value pack. Fits all XB4