Shimano FC-R8100-P Ultegra 12 Speed Power Meter Chainset - Superb quality and value from this dual sided power meter, offering all the precision and functionality of the Dura-Ace power meter, in a more affordable package. Scientific training requires accurate measurement and user-friendliness, and the new Ultegra R8100 power meter has both. Its dual-sided measurement is accurate within 2. 0 and zero offset calibration is a quick and easy process. Perhaps most importantly, its long battery life, easy recharge, and ANT+ and Bluetooth LE connectivity makes using and recording your workouts easier than ever. Shimano FC-R8100-P Ultegra 12 Speed Power Meter Chainset Features The Hollow Tech II 12-speed Ultegra chainset with integrated power meter offers an ideal balance of light weight and stiffness, making it the perfect choice for both enthusiast and competitive riders Accurately calibrated strain gauges are integrated inside the crank arm, this provides a stable measurement system through rotation from both sides for extremely precise data +/-2 accuracy of strain gauge measured power Bluetooth and ANT+ with wireless firmware update and data acquisition system Easily rechargeable integrated battery with fully waterproof reliable electric system Hollow Glide 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 12-speed HG chains for increased contact to provide greater efficiency and improved power transfer Industry leading Hollow Tech II cold forged 4 arm hollow cranks have been evolved for maximum rigidity while reducing weight Wide gear pitch spacing increases clearance between chain and leading teeth to provide compatibility to frames with O. L.D. 135 / 142 mm A wide range of chainring options and crank arm lengths are available to meet the needs of all riders and racing disciplines Hollow Tech II in