SHIMANO Ultegra 10-speed RD-6700A Rear Derailleurs Sizes Wide gear ratio with enhanced cable pull mechanism is compatible with 28T cassettes and compact cranks Stiffer, wide outer link design suppresses flex for sharp, precise shifts that are faster, smoother and more stable 11T sealed bearing pulleys run quieter and spin smoother 4 fluorine-coated link pivot pins minimize friction and increase shifting response Lightweight aluminum pulley cage reduces weight without sacrificing performance