Wolf Tooth headsets are machined here in our Minnesota shop with aircraft-grade 6061 aluminum. They are designed to be lightweight, strong, and durable. 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 IS headsets are for frames with molded-in internal bearing cups. Premium Headsets with Enduro stainless steel bearings have a lifetime warranty. Compatibility: Any frame that uses IS (Integrated Standard) headsets with 41mm upper and 52mm lower outer bearing 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). Upper assembly features: Ultralight Stem Cap with Integrated Spacer plus an aluminum bolt and a star nut. 7, 15, and 25mm stack height top cover options (7mm cover = 8mm total stack, 15mm cover = 15mm total stack, 25mm cover = 25mm total stack. O-ring seal prevents water intrusion around steerer tube. Custom-molded upper lip seal provides additional protection for upper bearing. Lower assembly features: IS lower headset consists of a bearing and crown race only. The crown race is black anodized and not visible when installed. Custom over-molded dual-lip seal on the crown race to protect lower bearing in the toughest conditions. Headset components precision machined in-house at Wolf Tooth from aircraft grade aluminum to ensure the highest level of quality.