The 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 riders hollowglide 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 conjunction with 11 speed hg ev chains for increased contact to provide greater efficiency and improv