Shimano Dura-Ace Di2 R9250 12 Speed Rear Derailleur With the Dura-Ace RD-R9250 Di2 12-speed rear derailleur, SHIMANO is literally stepping up a gear and taking its top electronic shifting group for road bikes to the next level. Whether minimum gear steps or maximum gear range: In combination with a matching SHIMANO 12-speed road cassette with up to 34 teeth, the 215 gram RD-R9250 rear derailleurs as master unit allows you to adjust your drivetrain even more precisely to your requirements. For this, the HG+ chain and tooth profile is also used for the first time in the road range, which improves the chain engagement and thus promises a smoother drivetrain power transfer and less wear. Reliable and crisp gear shifts are ensured by the proven Di2 technology, which has been further developed by SHIMANO and, together with a compatible brake/shift lever, now also transmits the shifting commands wirelessly to the rear derailleur. Cables are thus only needed for the connection to the battery, which can now be charged directly on the rear derailleur via a charging port. However, those who prefer wired connections can continue to connect the components with cables instead. Whats more, the shifting speed of the predecessor has been increased by up to 58 percent, according to SHIMANO. Of course, the 2021 Di2 generation also offers the option of customising shifter assignments and synchronising rear and front derailleur in different modes. Define the gears at which the front derailleur automatically shifts, or let the rear derailleur make compensating shifts as soon as you operate the front derailleur. Thanks to integrated Blutetooth and ANT+ connectivity, you can easily make all settings with your smartphone and the SHIMANO E-Tube app. Or you can quickly change modes at the touch of a button on the rear derailleur, where you can also read the battery status. That's electronic shifting at Dura-Ace level that's the SHIMANO Dura-Ace RD-R9250 Di2 12-speed rear derailleur! Details: Wireless electronic 12-speed rear derailleur Di2 wireless chip with low interference, high processing speed and low power consumption Increased shifting speed (approx. 58 % faster compared to the predecessor model) Compatible with Synchro-Shift: shifting front and rear derailleur with only one lever Program-controlled shifting movement: faster and smoother shifting with reduced risk of chain drop Shadow RD design: flat design for a clean look, stable shifting and resistance in case of a fall Compatible with Direct Mount Shifting cage made from carbon fibre reinforced composite material 4 fluorine coated connecting pins SD300 E-Tube Port: slimmer cables for less weight and easier routing 11-tooth pulley wheels with cartridge bearings Bluetooth LE compatible: can be wirelessly customised via E-Tube app for smartphone & tablet Compatible with ANT+: transmission of data (e.g. current gear) to compatible bike computers Universal cage length for up to 34 teeth Function key for quick change of switching modes, system configuration and battery level display Status LED for system information and battery level displays at the touch of a button Splash-proof charging port for charging the central Di2 system battery Also suitable for wired setup Technical details: Intended use: Road, TT, Triathlon Material: aluminium, carbon composite, stainless steel Gears: 12 Max. sprocket size: 2834 teeth Min. sprocket size: 11 teeth Total capacity: 37 teeth Compatible chains: HG 12-speed Slots: 1 EW-SD300 E-Tube port, 1 EW-EC300 charging port Function key: yes Weight: approx. 215 g.