The fsa orbit z number 9 semi integrated headset is ideal for use with headtubes that have an outer diameter of 50mm this headset has two deep cups made from forged crmo a tough yet lightweight metal that you can rely on to deliver a great performance the headset is a lightweight 1141g and comes in black a colour that will look good on any bike features of the orbit z number 9 semi integrated headset 1 18 36deg 36deg acb deeper cups for 50mm od headtube 1 18 steerer alloy t