The HollowTech II 10-speed Dura-Ace chainset offers the optimum balance of light weight and rigidity, making it the global choice for road racing's elite ridersShimano has raised the bar to a new level ofperformance with the development of a hollow outer chainring, giving vast improvements in rigidity and increased weight savingsThe hollow outer chainring has essentially removed outer chainring flex, hugely improving shift performance making it precise even under high loadThese industry leading HollowTech II cold forged hollow crank arms have been evolved to increase rigidity, reduce weight, and improve strengthThe teeth have been developed to work only in conjunction with the CN-7900 chain forimproved contact providing more efficiency and improved power transferThere is a wide range of chainring ratios and crank arm lengths available enabling customisation for all riders and racing disciplinesHollowTech 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 durabilityWeight including bottom bracket 725 grams