Mountain bikes have changed in the decade since the original Arch rim helped introduce the world to tubeless technology. With a 28mm wide asymmetric rim shape and ultra-strong 6069 alloy, today's Arch MK4 rim has evolved to match these more capable bikes. Through all the years of testing and refinement of this rim, one thing has never changed: versatility. Now more than ever, when you want a reliable rim that can handle every trail, the Arch MK4 is for you. The Arch MK4 rim is light enough to take XC racing but was born from research and testing on the Enduro World Series circuit, making it a great rim for anyone looking to improve both descending and climbing. Constructed of light and strong 6069 aluminum alloy, with a reinforced spoke bed and 28mm internal width ideal for 2.2-2.5" tires, the Arch MK4 can get you up the climbs easier and make the descent even better. The Arch MK4's BST-Asymmetric shape improves spoke angle, allowing for a stronger overall wheel build. Unlike most asymmetric rims that struggle with tubeless inflation and consistent airtight seal under hard cornering, the Arch MK4's shape is designed to equalize pressure for easy inflation and incredibly strong tire retention on both sides of the rim. Stan's patented Bead Socket Technology, combined with a stronger asymmetric design, light and durable 6069 alloy, and the perfect rim width for balancing control and weight, make the Arch MK4 your best choice for all-around riding. Powering up rocky switchback climbs or slapping berms on every descent, the Arch MK4 is ready for whatever you can throw at it.