With the bike on the workstand the night before a bikepacking trip, the Switch UDH Adaptor is the part that lets the Switch Rack work on a bike with a universal derailleur hanger. This replacement derailleur hanger takes the place of the frame's own UDH and pairs with the Switch Axle in 1 millimeter thread pitch. What Our Gearhead(R) Experts Are Saying:"With the adaptor in place, the Switch Rack went on without any fuss, and it stayed quiet and tight over a loaded weekend of rough gravel. The swap itself took one short evening on the workstand."