Shimano ultegra 6800 double cx 11 speed chainsetthe hollowtech ii 11 speed ultegra chainset offers an ideal balance of light weight and stiffness making it the perfect choice for both enthusiast and competitive ridersplease note bottom bracket is not included featureshollowglide hollow outer chainring gives vast improvements in rigidity by virtually removing outer chainring flex and hugely improves shift performance even under high load the chainring teeth have been developed to work in conj