When developing the Rear Axle, Wolf Tooth engineers knew that they wouldn&&';;t be able to get away with any old factory replacement part, even if it was made in Minnesota to aerospace standards. The Wolf Tooth Rear Axle uses a captive steel washer under the head to reduce friction on the dropout face. This protects your expensive frame, transfers more of the tightening torque to the clamping load for a stiffer interface, and prevents the axle from sticking or galling when you want to remove it. These are also great replacement options for lost or damaged stock axles. Always apply a small amount of grease to the washer and threads when installing. Compatibility 12mm Rear Thru Axle Axle length is compatible +/- 2mm Axle length is independent of hub dimensions. Please use the Axle measurement guide to find the axle length needed. Make sure to print it at 100% for accurate measurements. Make sure you match up the axle length, thread pitch, and thread length. All three dimensions are critical for proper fit.