FSA Orbit C-40-ACB 1.5 Headset (No 42/ACB). A combination of the other styles, tapered headsets will be used with a steerer tube that has a 1.1/8″ or 1.5″ lower diameter, and a 1.1/8″ upper diameter. Headsets for such frames and forks can be any combination of traditional, internal, or integrated headsets. It is very important to accurately measure the inner diameter of the headtube top and bottom to narrow down the headset model needed. In some cases, tapered headtubes can be used with a straight 1.1/8″ steerer tube if a reducing headset race is available for that headset Features: Steerer Tube OD: 1 1/8″ to 1.5″ taperedUpper Headtube ID: 42mmLower Headtube ID: 52mmFork crown seat OD: 39 8mmStack height: 8.9mm Angular Contact BearingsWeight: 83 4gBuy FSA Components from Chain Reaction Cycles, the World’s Largest Online Bike Store.