The Shimano 105 5603 10 speed GS Rear Derailleur is a good upgrade for and road or triathlon bike. The Shimano 105 5603 10 speed GS Rear Derailleur makes shifting almost effortless thanks to the light action spring. Plus, the 105's top pulley stays a uniform distance from each sprocket so shifts resonate with the plunk of exact gear engagement. The wide outer-pivot design increases rigidity for precision shifts every time. The Shimano 105 5603 10 speed GS Rear Derailleur is a great value since it has the same quality of construction as the Dura-Ace and Ultegra derailleurs, and only trades a few grams of weight. OneTri is one of the premier retailers for the Shimano 105 5603 10 speed GS Rear Derailleur.
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