The fastest shifting rear derailleur across Shimano's widest ever Dura-Ace gear range, the RD-R9250 is capable of both race wins and personal bests. The Dura-Ace RD-R9250 integrates the system charging port and a wireless connectivity unit all while delivering super-fast, precise shifting worthy of any podium. Engineered with a single cage length, this derailleur shifts across cassettes with gear ratios from 11-28 to 11-34 - bringing new versatility to the world's best road component groupset. Shimano Di2 Electronic Drivetrain Performance Thanks to its lightning-fast, accurate, and reliable shifting performance, Di2 puts riders in complete control and ensures a seamless interface between the cyclist and bike like never before. Creating and continually improving the world's best shifting is a complicated undertaking requiring constant technological advancements. From hardware to software, Shimano Di2 technology is on the cutting edge, striving to deliver the best rider experience possible now and in the future. Shimano E-Tube Compatible E-Tube is Shimano's “service” that uses websites or apps to maximize the enjoyment of riding a bicycle by connecting the riders, the bicycles and Shimano. Shimano's genuine application E-Tube Project for Mobile allows you to customize your bike, update firmware, and maintain it by connecting it wirelessly to your bike. You can also get more detailed bike maintenance by connecting to your bike by wire with E-Tube Project via the Windows V4 application. Direct Mount Compatible Rear wheels are easier to remove with a mounting option for Shimano Shadow rear derailleur (RD) and Shimano Shadow RD+. The direct mount feature is designed to suit a wide range of contemporary frames with large-section chainstays, in particular, mountain bikes with thru-axle dropouts. Shimano Shadow Low-Profile Rear Derailleur The mechanism rear derailleur, Shimano Shadow RD, is intended for more aggressive riding. Its super low profile design carries many benefits. Because of its low profile and single tension construction, the derailleur does not hit the chain stay in rough riding conditions. The result is smooth and silent performance.