The Shimano Dura-Ace Di2 RD-R9150 11 Speed Rear Derailleur is quick, smooth and effortless, making for unmatched drivetrain efficiency. Shimano Dura-Ace Di2 RD-R9150 11 Speed Rear Derailleur Features Digital Integrated Intelligence or Di2: with programmed automatic motion at the touch of a switch the Dura-Ace Di2 rear derailleur is quick, smooth and effortless, making for unmatched drivetrain efficiency Programmed automatic motion at the touch of a switch makes this derailleur quick, smooth and effortless to shift Synchronized Shift designed, developed to choose the next biggest or lowest gear ratio irrespective of whether a gear change needs to be made by the front or rear derailleur Wireless data network system unit is integrated into mech The removal of traditional mechanical cables in favour of electrical wires not only eliminates poor shifting caused by contaminates, corrosion and stretching Low profile Shadow derailleur design Derailleur contains a saver (fuse) function, where the inner structure is protected from strong impacts 11-30T wide gear ratio capacity will cater for compact setups as well as the traditional road double Full carbon fibre inner and outer pulley plates enhance rigidity and reduce weight Titanium B axle bolt for further weight savings High tolerance cold forged aluminium link plates and body construction is extremely light and durable Four self-lubricating micro-machined fluorine-coated link pivot bushings provide low-friction shifting Pulleys are made of tough DuPont Zytel for longer life and less chain noise Direct mount compatible 11-speed E-tube Di2 compatible Max front difference: 16T Total capacity: 35T Weight is 204 grams