The Supercross BMX Flush mount 20mm BMX axle is designed to work with all 20mm BMX hubs with the std. 100mm spacing. The Supercross BMX Flush Mount axle is available in 2 sizes. 1 to fit Cro-mo dropout Forks and 1 to fit thicker Carbon/Aluminum fork dropouts. it is built from 7075 t-6 Aluminum to be ultra strong while being superlight. The Flushmount design keeps the front of your bike looking clean and is simple to install your wheel with a 6mm allen wrench rather than having to have that big bulky crecsent wrench.