A new level of performance for Shimano 12-speed road rear derailleurs. Wide 36T-compatible 12-speed Di2 rear derailleur. Receiving the wireless shifting signal from the shift lever, the Shimano 105 rear derailleur completes a shift in the blink of an eye with its high-performance motor and optimised link structure. This is the hub of the Di2 system, with the charging port, indicator LEDs, adjustment switches and more integrated into a compact package. A low-profile design reduces damage from contact and falls.105 Shadow design with Di2 technology, shifting is easy and precise - just a light touch, as soft as a mouse click, is sufficient for the front or rear derailleur to instantaneously select the correct gearThe rear derailleur is now the brains of the system with wireless connectivity to the shifters. It acts as the point the system is charged, provides ANT+ connection to 3rd party devises and replaces the handlebar junctionButton on the derailleur for Di2 operations, and LED light