These lower headset cup extenders allow you to adjust the geometry of your bike frame by increasing the effective fork length by 10mm. They allow you to do things like use a rigid fork on a suspension-corrected frame or use a fork with a shorter axle-to-crown height rather than what the frame was designed to use. They can also be used to increase the bottom bracket height and lower the headtube angle. 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. These EC headsets are for frames with external bearing cups, which places the bearing outside of the frame. COMPATIBILITY Any frame that uses an external cup headset with a 49mm head tube inner diameter. Uppers and lowers sold separately. Enduro stainless steel sealed bearing included. FEATURES Custom molded dual-lip seal on the crown race to protect lower bearing in the toughest conditions. Service and additional parts available. SPECIFICATIONS Weight: 68g Material: 6061-T6 aluminum 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.