Add-ons
In order to provide a cable stop for front cantilever brakes or centerpull brakes, a hanger may be incorporated into the headset, either as part of the washer between the top race and the lock nut in the case of threaded headsets, or as part of a spacer between the top race and the stem in the case of threadless headsets.
Read more about this topic: Headset (bicycle Part)