The new wireless Di2 platform ensures fast and smooth shifting at the derailleur. Additionally, it offers a choice between manual shifting and synchronized shifting assist modes – SEMI-SYNCHRO or FULL-SYNCHRO – which feel like your own personal assistant! In SEMI-SYNCHRO mode, the rear derailleur automatically adjusts to avoid large jumps in gear ratio, allowing you to maintain your cadence and rhythm. In FULL-SYNCHRO mode, the rear derailleur and front derailleur work harmoniously together, so you always have the right gear engaged and no longer have to worry. Seamless communication with the derailleur combined with programmed control of the chain guide minimizes the risk of chain drop. The maximum number of teeth is 50-52. It’s entirely up to you how often you want to think about the gear ratio!