ULTEGRA's new FC-R8100 crank maintains the same quick, precise front shifting and efficient power transfer that Shimano riders have grown accustomed to, but with even more crank arm length options. Spanning 160 to 175 mm in length, ULTEGRA cranks now cater to smaller riders, triathletes, and cyclists curious about shorter crank arms. HOLLOWTECHA lightweight crankset not only reduces the bike’s weight, but decreases rotating mass to aid in acceleration. The challenge is to reduce the weight of the crank without reducing its strength and rigidity. SHIMANO’s advanced forging technology has solved the problem through the HOLLOWTECH crank. Just like high quality frame tubing, a hollow crank arm can provide amazing strength and rigidity at very lightweight. HOLLOWTECH IIThe addition of HOLLOWTECH II technology integrates the bottom bracket axle with the right crankarm for more stiffness and a weight savings to achieve a high-dimensional balance. Its outboard bottom bracket bearing system provides better weight distribution and more pedaling stability, allowing for more efficient power transfer. The HOLLOWTECH II crankset has been developed by pursuing the optimum balance of stiffness & rotating performance in a lightweight and beautiful crankset design.High Precision Sealing Moreover, HOLLOWTECH II crankset has a high-precision sealing in the bearing area to increase durability maintaining the excellent rotating performance for long periods.