The big news with the Ultegra R8000 group was the move to max rear derailleur of capacity of 11-34T. The increased call for overall drivetrain range for road, gravel, road, and endurance cycling prompted Shimano to fully invest the R8000 drivetrain with more capability. You get the standard popular cassette options at the actual R8000 level up to 11-32T, but Shimano also developed this slightly stronger 11-34T option- which can be run with both road and mountain HG11s freehubs. The 11-34T, Ultegra quality option is this CS-HG800 11-Speed cassette.

The Ultegra RD-R8000 and Di2 R8050 Shadow Rear Derailleur comes in two sizes, SS (short cage), and GS (mid-cage). Cassettes up to 11-30 are compatible with the SS version, while the 11-32 and 11-34 requires the GS model. This set-up is also fully compatible with Dura-Ace R9000 / R9100 so if you need more gearing on your Dura-Ace bike, you can opt for the Ultegra R8000 GS rear derailleur and the wider range cassette options.

Shimano delivers an incredible amount of systems engineering in the shape, tooth design, and shifting gates in their cassettes that nothing shifts smoother, faster, or more reliably. The HG800 cassettes feature precision-made nickel-plated steel cogs with an anodized that wear slowly and resist corrosion. Two groupings of 3 and 2 respectively are pinned to anodized aluminum spiders, while the remaining 6 cogs are individual. An anodized aluminum lockring holds the assembly together when mounted on the freehub. If you install the cassette yourself, take a long look at how each cog is made, and how each cog is aligned to it's neighbors. So much of what we take for granted with Shimano cassettes is intricately detailed in plain view, and no company holds as many shifting related patents as Shimano does.