The XX1 2. 1 is the latest iteration of SRAM's XX1 X-Horizon Derailleur. The design is based on a horizontal parallelogram that moves the body on a horizontal plane rather than up and down. By limiting the movement of the derailleur, ghost shifting becomes a non-issue. Additionally, there is a small offset between the upper and lower pulleys. No, they aren't misaligned; they are designed specifically to provide a constant chain gap throughout every one of the rear gear ratios. This means smooth, consistent shifting whether you are shifting up or down. The body is fabricated from carbon fiber to maximize strength to weight.