Shimano CS-R9100 is an 11-speed Dura-Ace road cassette for Shimano HG freehubs, built for riders using Shimano-compatible road drivetrains. The 11-25T version is the tightest common range in the R9100 line, which makes it a good choice for racing, flat-to-rolling terrain, and riders who want smaller jumps between gears for steadier cadence control.

This cassette uses a lightweight carrier with titanium sprockets on the larger cogs, helping keep weight low while maintaining the stiffness needed for clean shifting under load. It fits Shimano HG 11-speed road systems and is designed to pair with Shimano 11-speed chains such as HG-EV/HG-X11. The 11-25T ratio gives closer spacing than larger-range cassettes, but it also offers less climbing assistance than 28T or 30T options, so it suits riders who prefer speed and cadence consistency over easier low gears.