Specially-designed 2WD/4WD back tires with 12mm interior hex. The center countersunk area had been indeed redesigned to position the wheel nut more deeply. Precision fit, well suited for high-competition race. Made out of versatile, durable product to withstand impacts. The medial side of wheel is aerodynamic for optimum performance. Special options that come with the wheel are visible through inside: reinforcement ribs to help make the tires as stable as you can and expel deformation.