For optimum wheel strength and reliability, Shimano's Dura-Ace Rear Freehub is made of cold-forged aluminum with an oversize shell, sturdy flanges, a titanium freewheel body and a 15mm internal axle. Inside, diamond-polished bearing races and stainless-steel ball bearings minimize rolling resistance, while high-tech seals keep out water and dirt for maximum durability. This hub also features tool-free bearing adjustment for easy maintenance plus a light and strong aluminum/steel quick-release skewer.