The 12-mm Thule adapter Shimano E-Thru 12x1.5 is for bicycles with a 12mm Shimano e-thru axle. If your new Thule cycle trailer can't be attached to your bicycle, you might just need this adapter.Before buying, it is important to find out what axle your bike has in order to find the right adapter (some axles had the measurements and data stamp on them)