The iRiX headset is the ultimate headset system for your bike. Inspired by the Greek goddess Iris, the personification of the rainbow, and the Roman numeral IX, the iRiX embodies the core DNA of Industry Nine. Featuring bearing cups, top covers, and top caps that are machined, anodized, and laser-etched using US-sourced 7075 aluminum in Asheville, NC USA. With every common modern size and 11 lustrous colors available, there is an iRiX to complement any bike build. Designed with ease of service and bearing life in mind, the iRiX headset boasts features such as split crown races and top cover compression rings, making installation and removal tool-free. Two available top cover heights allow riders to hone their perfect fit or aesthetic, while the top covers boast an integrated adjustable shim stacking function to dial in the ideal headtube clearance on IS applications. To keep the sealed bearings contaminant-free, the crown race and top cover employ removable and replaceable silicone lip seals, ensuring a smooth ride every time. The iRiX headset uses industry-leading 440c Stainless Steel bearings with a lifetime warranty, guaranteeing that your turns will remain as smooth as on day one. And with the custom color selection available for lower cups, upper cups, top covers, and top caps on EC and ZS models, as well as top cover and top cap on IS options, you can create a one-of-a-kind look for your bike. Details Position: Both top and bottom Style: Zero Stack (ZS4428.6/ZS5640) Upper Headtube Bore: 44mm Lower Headtube Bore: 56mm Top Cover Height: 5mm, 15mm