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-The removal of traditional mechanical cables in favour of electrical wires not only eliminates poor shifting caused by contaminates, corrosion and stretching, but provides effortless gear shifts-Derailleur contains a saver (fuse) function, where the inner structure is protected from strong impacts-11-27T 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 bushins provide low-friction shifting-Pulleys are made of tough DuPont Zytel for longer life and less chain noise-10-speed Dura-Ace Di2 compatible-Weight is 225 grams