The new Chorus groupset is fully compatible with the cassettes from the Record and Super Record 2x12-speed groupsets (11-29 and 11-32) but also introduces a new cassette specification of 11-34. NB - the 11-34 Chorus cassette cannot be used with a Record or Super Record rear derailleur.
The new 11-34 cassette offers cyclists even more versatility and a greater choice and autonomy in terms of available gears.
Chorus 12-speed now therefore offers a total of three cassette options:
Same width as the 11-speed cassette: Totally compatible with wheels and frames.
The two bigger sets of three in a single-block piece: It eliminates energy dispersion.
Surface treatment: It increases durability and improves smoothness.