Specially-designed 2WD/4WD back wheels with 12mm inside hex. The guts countersunk area was in fact redesigned to position the wheel nut more deeply. Precision fit, perfect for high-competition race. Created from versatile, durable product to withstand effects. The inside connected with wheel is aerodynamic for maximum performance. Unique options that come with the wheel are visible through inside: reinforcement ribs to help make the tires as stable as you possibly can and expel deformation.