These front derailleur hangers, compatible with Traildonkey 2.x and 3.x, allow the use of subcompact 2x (say: “two by”, f.k.a. “double”) chainring combinations by extending the usable front derailleur hanger range downwards. They are compatible with standard 53/39 road chainrings all the way down to 46/30 micro compact chainrings. Pick one up, ditch those roadie gears, and opt smaller on your Traildonkey.