The uninterrupted shifting experience of the Shimano Ultegra CS-R8101 12-speed cassette range lets you climb, sprint, or cruise without stopping to think about your next gear change. Larger driving cogs maximize drivetrain efficiency and create compatibility with both Shimano 11 and 12-speed freehub bodies. Shimano HYPERGLIDE technology is integrated to provide seamless shifts both up and down the gear range.