The 12 speed 105 R7100 chainset features aluminum cranks with hollow arms for lightweight, rigidity, and durability. The newly designed crank arms offer an optimized balance between lightweight and efficiency. The chainset, formed with hollow aluminum technology, is anodized with a beautiful gloss black anodized finish, giving it a luxurious look. The resin ribs on the back of the chainrings are Shimano 105's unique structural design that achieves both thorough weight reduction and crisp shifting performance.   Features Optimal balance of stiffness, strength, weight and rotational performance. Hollowtech II structure cuts weight yet maintains strength for better power transfer. Gear combination: 50-34T, 52-36T. Q-factor: 148 mm.