Shimano 105 RD-5700 Rear Derailleur - $58.95

As 105 adopts all of Shimano's best features year after year, the latest 105 components eclipse Dura-Ace and Ultegra from just a few years ago that, at the time, cost twice what today's 105 does. Case in pointthe Shimano 105 RD-5700 Rear Derailleur.The pivots on the body of the 5700 derailleur are wider than the previous model, and are thus better to resist flexing and twisting when you shift under load. That's the secret sauce for better, faster shifting. As always with 105, this is a trickle-down design from Ultegra. So that ultimately means that it will work with 6700 shifters without problem. It will also work with older Ultegra (6600 and SL) shifters. Compatibility aside, the differences between this derailleur and a Dura-Ace changer are many. The most obvious is that this 105 derailleur isn't as light. There's more metal, and the pulley cage is made from aluminum rather than carbon fiber. Also, the pulleys run on bushings instead of bearings. The cage design, along with the pulley cage placement, allows this derailleur to work with cogs as tall as 28 teeth -- nice for those who want a really low gear, yet still have fast shifting. The Shimano 105 RD-5700 Rear Derailleur is designed to work with double chainrings and 10-speed cassettes. The total chainwrap capacity is 33 teeth, The limit screws are on the back of the derailleur, just above the barrel-adjuster, and can be accessed from the rear. - $58.95