Just when you thought shifting quality and reliability couldn't get any better, Shimano ups the ante with their Dura-Ace Di2 9070 rear derailleur. Some call the Dura-Ace Di2 9070 a "luxury group", but we have yet to meet a pro who didn't want ultra-reliable, precise, lightning-fast shifts across an 11-speed cassette with just a button click.
The 9070 rear derailleur is now more compact and about 10 grams lighter than its predecessor with sleeker lines no motor bulge. The 9070 series derailleurs use E-tube connections to simplify installation. The E-tube connections are smaller than 7970 and basically a waterproof plug and play system. Like the 7970, the 9070 has an automatic crash protection feature that can save a large repair bill if the right side of your bike takes a hit.
For 11-speed electronic Di2 only. Maximum largest rear cog 28t