RockyMounts DriveShaft SD RockyMounts DriveShaft SD is a 12mm, 15mm, and 20mm thru-axle bike rack carrier for truck bed channels found in Toyota Chevy GMC and Nissan trucks. Product includes 15mm shims. 12mm shims sold separately RockyMounts DriveShaft is the first on the market with the ability to carry 12/15/20mm thru-axles and to securely lock your bike The DriveShaft SD also comes with a 9mm dummy axle quick release to fit standard bike axles 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 12/15/20mm thru-axles Comes with RockyMounts locks and keys