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. 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 the steerer tube. - Custom-molded upper lip seal provides additional protection for the upper bearing. - bearing top cap outer diameter 45.8 mm