The Di2 dual-control lever from the lightweight DURA-ACE R9100 series has also been optimized and now offers more grip and balanced ergonomics with adjustable reach settings for improved shifting (and braking). The more defined clicking sensation gives you a feeling of greater control with every gear change. Synchronized Shift enables more efficient gear changes while riding. This function provides numerous benefits such as faster, more precise shifting under all riding conditions and minimizes strain on the drivetrain. When Synchronized Shift is activated, the rear derailleur and front derailleur can be controlled with just one switch. With fully activated Synchronized Shift, the front derailleur detects the position of the rear derailleur and automatically shifts to the most efficient gear with the best chain line, so you never again have to worry about front shifts or trim adjustments. With the semi-Synchronized Shift function activated, you can manually shift the front derailleur, giving you optimal control in selecting the best gear combination for your riding style. The system automatically makes the necessary corrections by shifting into the correct rear gear with the best chain line.