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 ZS headsets are for frames with internal bearing cups that are pressed into the frame. 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. - 6, 15, and 25 mm stack height top cover options (6mm cover = 6mm total stack, 15mm cover = 15 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.