These Red Dirt Derby precision machined and polished axles are grooved in order to reduce speed robbing friction caused when the wheel is in contact with the axle. The machining process also ensures that the axles are perfectly straight for the truest roll. Lastly these axles were engineered with an increased diameter in order to reduce wheel wobble. These are not original BSA nails, these are precision machined, perfectly straight axles. Check your rule book.