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 option t 05 headset is a semi integrated headset that is design to fit 50 to 55mm tapered oversized diameter head tubes the cups are alloy which have angleset adjustment on them 05 degrees and fit 1 18 steerer