The Hollow Tech II 10-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 the CN-7900 & CN6700 chains for increasedcontact to provide greater efficiency & enhanced power transfer Industry leading Hollow Tech II cold forged hollow crank arms have been evolved to increase rigidity, reduce weight & improve strength A wide range of chainring options & crank armlengths 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 interface