SRAM's XX1 is a fresh approach to drivetrain designs that builds on proven, and preferred, principles of established riders and racers alike. One-by setups are nothing new, but none have offered the ratio spread, chain retention, and performance driven technology that this 11-speed group does. The single front chainring, in fact, packs as much design time as some multiple-cog cassettes. Take a look at the tooth profile, and its shape is decidedly unique. This isn't your run of the mill single-speed ring.