Aside from some slightly modified aesthetics and a 10g reduction in weight, the Shimano Dura-Ace Di2 FD-R9150 11-Speed Front Derailleur carries over the high functioning precision of its 9070 predecessor. While the new 9150 rear derailler gets all the attention for its mountain-inspired changes, the front derailleur sits stealthily by as the brains of the Di2 system, ensuring fast, reliable, and customizeable gear shifts whether you're off to the coffee shop for the Sunday social ride or hammering the pedals at the pointy end of the peloton. The front derailleur has always been our favorite component of the Di2 series, reinforced by years of mechanical systems throwing chains at inopportune moments on climbs and winding up for sprints. Di2 makes thrown chains a part of history with fast, silent, and accurate chain movement boosted by Shimano's automatic trimming function. This feature adjusts the position and angle of the front derailleur, on-the-fly, and eliminates the possibility of dropping the chain under heavy shifts up or down the chainrings, regardless of how cross-chained that you may be. This function also prevents the mere thought of chain rub for a smooth, quiet ride in every gear combination.