This axle is designed to work with our 41mm narrow glide trees or any trees that are around 7in on center and the early style Panhead/gen shovel tapered sliders. This Axle is machined from stainless steel so rust is not an issue. This axle is 3/4 (.75in) diameter. The way this axle is designed you can easily turn it down to 5/8 (.625in) or any size in between. K model /early sportster hubs are 17mm (.669in) so you can turn it down to that size as well.