Fsa is the world leading headset manufacturer and the core of their product line with many years of experience they understand that multiple dimensions and exacting requirements are a must when it comes to headsets the fsa orbit xtreme pro 15 reducer headset is a conventional threadless headset has forged and cnc machined from 7075t6 aluminium cups which is made to fit frames with 55mm od head tubes fsa has designed this headset to reduce down to fit 1 18 steerer so you can run your old