Single chainring, wide range mountain bike drivetrains have more than demonstrated their viability- for many riders this is the new gold standard. SRAM's 12-speed Eagle group moves the needle even further with a 1x crankset and a 500%+ range in 10-50, 10-52 options. This range gets you within about 8--15% of the effective range of most wide range mountain bike doubles, but with the simplicity and reduced weight of a single shifter and no front derailleur. SRAM takes full advantage of the XD Driver standard, as well as their innovative XD-Dome large cog technology. In this XX1 Eagle version, you also get a Ti-Nitride gold finish in the bottom 11 machined chromoly cogs. While it looks spectacular, aesthetics didn't drive the decision, friction reduction and longer wear did. At just 352 grams, the 10-50t is remarkably lightweight for what it actually offers- ridiculous range!

SRAM machines the 11 smaller cogs and carriers from a single block of chromoly steel. The company has been doing this since the first PowerDome 10-speed Red cassette and the process has only gotten more refined. Stiff, strong, and light, this assembly slides onto the 11-speed XD Driver- no new freehub or wheelset if you already have an XD equipped version. The XD-Dome Eagle design adds a machined aluminum 50T, 52T cog with a spline center that is affixed to the steel section. You simply slide the entire assembly onto the XD Driver body, lining up the rear splines, and then tighten the internal lockring that holds the cassette in place. Though the spline depth for the cassette tool is slightly deeper than an some older cassette locking tools that use the 12-notch 23.mm diameter (think SRAM and Shimano standard cassette lockrings), most newer tools have a deep enough spline zone to make the interface.

From a shifting perspective, SRAM has spent year of R+D on developing and improving on how the chain and cassette teeth interact. The X-Glide 2 system was optimized for the narrow 12-speed Eagle chain and the loads and angles created by the design. The new, integrated and clocked tooth profiles provide quick, precise, power-on shifting performance throughout the gear range, and increase chain retention on larger cogs. With the added Ti-Nitride coating, reduced friction shifting is not only faster and smoother, but also quieter and results in greater wear capability while preventing corrosion. The technology, engineering and performance of the XG-1299 Eagle 12-Speed Cassette must be experienced first hand, and many XX1 11-speed riders have been blown away by the differences in the drivetrain overall and how smoothly the shifting is with these incredible massive range cassette.