IFMAR appropriate size, specially-designed 2WD/4WD rear tires with 12mm internal hex. The guts countersunk area had been redesigned to put the wheel nut deeper. Precision fit, ideal for high-competition race. Created from versatile, durable material to withstand effects. Along side it for the wheel is aerodynamic for optimum performance. Medium hardness. Special options that come with the wheel are noticeable from inside: reinforcement ribs to really make the tires as stable as you can and expel deformation. Pair of 5 pairs (10 pcs) the cost of 4 pairs. Outstanding value pack. Fits all XB2 & XB4