RockyMounts DriveShaft Thru-Axle Adapter RockyMounts DriveShaft is thru-axle adapter that can fit 12m, 15mm, and 20mm axles The only thru-axle e adapter on the market that securely locks your bike Fits standard fork mounts from RockyMounts, Yakima, and Thule bike racks Its wide mouth opening creates easy loading, holds tight with adjustable cam lever and comes with snap in nylon shims to prevent the axle from being unscrewed and gives the ability to switch between 12mm, 15mm, and 20mm thru-axles Comes with 15mm shims and RockyMounts lock and keys. 12mm shims sold separately