Finally, Shimano has produce a road rear derailleur that will officially work with up to a 30-tooth rear cog. This SS or short cage version can handle 34 teeth of chain wrap (total difference in chainrings plus difference in cassette cogs) meaning it will work with 50-34 chainrings and a 12-30 cassette. So now you can spin up those steep hills with excellent shifting performance too.
The Shimano Ultegra 6700 components are inspired by the top-end Dura-Ace 7900 line helping the Ultegra 6700 to jump ahead in quality and performance. The Shimano Ultegra 6700 rear derailleur features increased gear capacity. It can handle wide gear ratios including a 50/34 with a 12-30. The outside portion of the derailleur cage has been made wider to reduce deflection for more precise shifting. It is compatible with all Shimano 10-speed road systems.