RockyMounts Driveshaft HM Bolt-On thru-axle bike rack RockyMounts DriveShaft HM is a 12mm, 15mm, and 20mm thru-axle truck bed bolt on system Base flanges designed for a "do it yourself" bolt on installation into any surface 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 Includes 15mm shims. 12mm shims sold separately Comes with RockyMounts locks and keys