With several years of development and working closely with professional teams you can expect extreme accuracy from Shimano's first fully integrated power meter HollowTech II 11-speed Dura-Ace chainsetAccurately calibrated strain gauges are integrated inside both left and right crank arms, this provides a stable measurement system through rotation from both sides for extremely precise data+/-2% accuracy of strain gauge measured powerBluetooth and ANT+ with wireless firmware update and data acquisition systemEasily rechargeable integrated battery with fully waterproof reliable electric systemThese industry leading HollowTech II cold forged hollow crank arms have evolved to increase rigidity, reduce weight, and improve strengthThere is a wide range of Dura-Ace chainring ratios available seperatlyHollowTech II integrated bottom bracket design uses a wider bearing placement and larger axle diameter for increased stiffness and efficiencyBottom bracket seal design has a minimal bearing interface gives superbly smooth rolling and increased durability