SRAM XX1 Type 2.1 11 Speed Rear DerailleurSRAM XX1 Type 2. 1 11 Speed Rear Derailleur Offering the best in shifting performance and reliability the SRAM XX1 Type 2. 1, is the ideal rear derailleur for trail and enduro mountain bikes. Precise shifting: The SRAM XX1 rear mech features the X horizon horizontal parallelogram design with offset pulleys that keeps a constant chain gap across all 11 gears. This limits all movement to the horizontal access which reduces shift force for fast, precise