The Dura-Ace 10-Speed rear derailleur has a redesigned Wide Link design with a wider pivot placement between the two parallelograms meant to deliver crisper shifting under heavy-load situations. The wider pivot has the added benefit of increasing the long-term durability of the derailleur. Even after thousands of miles, the crispness of the shifting should still feel "as new." And, by the way, the 10-speed rear derailleur is compatible with 9-speed drivetrains too. MSRP $159.99.