Shimano Ultegra 10 RD-6600-GS Rear Derailleur - Triple

"Redesigned for 2005 with a new look and 10-speed capabilities. Precision shifting for narrowly spaced 10-speed cassette sprockets. 11-tooth pulleys alternate contact with chain links, reducing chain wear, and the larger pulley diameter runs smoother and lasts longer. Low-friction Advanced Light Action design reduces shifting efforts. Max. sprocket: 27TMin. sprocket: 11TFront difference: 23TTotal capacity: 38TWt: 219g."