Wolf Tooth headsets are machined here in our Minnesota shop with aircraft-grade 6061 aluminum. They are designed to be lightweight, strong, and durable. Premium Headsets with Enduro stainless steel bearings have a lifetime warranty. Our headsets have three levels of industry-leading custom sealing to protect bearings from the elements and prolong the life of the headset. Available in a variety of colors. These ZS headsets are for frames with internal bearing cups that are pressed into the frame. COMPATIBILITY Any frame that uses ZS (Zero Stack) headsets with 44mm upper head tube inner diameter. Uppers and lowers sold separately. Enduro stainless 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 aluminum 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). FEATURES Ultralight stem cap with integrated spacer plus an aluminum bolt and a star nut. 6mm top cover = 6mm total stack. O-ring seal prevents water intrusion around steerer tube. Custom-molded upper lip seal provides additional protection for upper bearing. SPECIFICATIONS Weight: 55-58g Material: 6061-T6 aluminum Stem Cap Bolt Torque spec: 2-3 Nm with light grease on threads only Made in the USA The Story Wolf Tooth was founded to design and manufacture precision cycling products that emphasize function, performance, and reliability to meet the needs of our fellow racers and riders. We are a group of cyclists in Minneapolis, Minnesota that spend a lot of time talking about bike components. Like most detail-obsessed riders, we're always looking for new products that could make our bikes lighter, faster, more versatile, or more reliable. We pride ourselves on delivering premium products of the highest quality.