The Hollow Tech II 11-speed Ultegra chainset offers an ideal balance of light weight & stiffness making it the perfect choice for both enthusiast & competitive riders Hollow Glide hollow outer chainring gives vast improvements in rigidity by virtually removing outer chainring flex & 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 & enhanced power transfer Industry leading Hollow Tech II cold forged 4 arm hollow cranks have been evolved for maximum rigidity while reducing weight A wide range of chainring options & crank arm lengths are available to meet the needs of all riders & racing disciplines Hollow Tech II integrated bottom bracket uses a wider bearing placement & larger axle diameter for increased stiffness & efficiency Hollow Tech II integrated bottom bracket seal design has minimal bearing interfaceensuring smooth rolling & increased durability