Shimano revamped it's workhorse Ultegra 6600 line and dubbed it Ultegra SL. With a new ice grey finish and a weight savings of over 70 grams over the whole group, Ultegra SL adds yet another high card to Shimano's already stacked hand. The 6600G SS rear derailleur is the short cage version, and is compatible with Shimano 9 and 10 speed groups (with the exception of Dura Ace 7900).