Warning not compatible with pre 2015 groupsetsthe new shape of the external components allows the rear derailleur to move efficiently to give maximum performance at any angle a new internal design keeps the chain closer to the cassette to ensure better power transmission and a more positive drive whilst allowing the component to move along a trajectory that perfectly follows the curve of the sprockets on both the 11 23 cassette and the new 11 29 a better chainsprocket interface also gives