The Wolf Tooth Performance Zero Stack Headset is machined in the USA from aircraft-grade 6061 aluminium, to ensure a lightweight, strong, and durable design.The headset uses Enduro chromium steel bearings with a black oxide treatment for superb durability and high load capacities.The headset has three levels of superior custom sealing to protect bearings from the elements and prolong the life of the headset.The Performance headset comes with a 1-year warranty. Key Features: Any frame that uses ZS (Zero Stack) headsets with 44mm upper and 56mm lower head tube inner diameter., Uppers and lowers sold separately., Enduro black oxide steel sealed bearings included on both the upper and lower., Upper headsets ship with a star nut which can only be used on forks with steel or aluminium steerer tubes. For forks with carbon steerer tubes you will need a compression plug (sold separately). (Never use a star nut on a carbon steerer tube) ,1-year warranty., Weight: 55-58g, Material: 6061 aluminium, Made in the USA,. Upper Assembly Features: Ultralight Stem Cap with Integrated Spacer plus an aluminium bolt and a star nut., 6mm top cover = 6mm total stack., O-ring seal prevents water intrusion around steerer tube.,Custom-moulded upper lip seal provides additional protection for upper bearing..