The largest three cogs on the new Dura-Ace cassette are supported by a separate cold-forged aluminium alloy carrier, as are the next two sprockets.
This increases stiffness and reduces weight – as does the fact that the largest four cogs are made from titanium. All this means that the cassette weighs in at a paltry 185g.
Shifting performance up and down is almost always smooth and positive, although sometimes the transitions are so smooth you catch yourself wondering whether it has changed gear at all.
The cassette is available in eight different sizes: 11-21t, 11-23t, 11-25t, 11-27t, 11-28t, 12-23t, 12-25t and 12-27t.