IFMAR appropriate size, specially-designed 2WD/4WD back tires with 12mm inside hex. The middle countersunk area was redesigned to place the wheel nut more deeply. Precision fit, well suited for high-competition racing. Produced from flexible, durable product to withstand impacts. The medial part related to wheel is aerodynamic for optimum performance. Medium hardness. Unique options that come with the wheel are noticeable from inside: reinforcement ribs to really make the tires as stable as you possibly can and eradicate deformation. Wide range of 5 pairs (10 pcs) the price of 4 pairs. A fantastic value pack. Fits all XB2 & XB4