The new SRM PowerMeter 11-Speed is the next generation of seamless drivetrain integration for Shimano groupo users and Power enthusiasts. Improving over the 7900 series SRM PowerMeter, the 11-Speed now boasts 3000 hours of battery life! Electronic shifting systems make gear changes faster and virtually eliminate missed shifts, but the forces on the chain rings are much higher than with mechanical derailleurs. With this in mind Shimano developed new Dura-Ace 9000 chain rings which are 20% stiffer than previous rings. This not only benefits the shift, but also in power transfer from the crank arm through the spider and into the drivetrain. If you ride Shimano DuraAce 9000 mechanical or Di2 electronic, you will benefit from increased power transmission! Available models: SRM-Shimano 11-Speed: 110mm BCD (53/39), (50/34), (52/36) CONFIRM YOUR SIZE WHEN YOU MADE THE CHECKOUT DELIVERED TIME FOR THESE PRODUCT 4 WEEKS