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 cf 40 tapered headset is an integrated headset to fit head tubes that are tapered the bearing are 45 x 45d angular contact bearings that sit flush in the frame with head tube outer diameter of 46mm at the top and 56mm at the bottom the alloy top cap is 9mm gives you