Boasting a unique four arm design with a hollowtech ii construction for added stiffness and reduced weight the shimano dura ace fc 9000 bicycle chainset 53 39t has hollowglide chainrings for smooth and precise shifting even under a heavy load lm features shimano dura ace fc 9000 bicycle chainset 53 39t four arm design for optimum stiffness and reduced weight hollowtech ii cold forged hollow crank arms help to improve strength hollowglide chainrings improve shifting performance