There are two different types of precision machined and polished axles in this set -two that are bent 2.5 degrees in order to allow for steering of your derby car (rail riding for your back wheels) and two that are straight. The machining process ensures that the axles are perfectly straight for the truest roll. Both sets of axles were engineered with an increased diameter in order to reduce wheel wobble. They have an increased diameter where the axle engages the wheel for reduced speed-robbing wheel wobble. These are not BSA nails, these are precision machined and bent axles. Check your rule book.