All new 120 engagement Whistler cassette hub is our most responsive cassette to date. Features a lightweight 6061-T6 aluminum hub shell, straight 14 mm heat-treated CRMO axle w/ allen insert for easy removal. 2 large sealed bearings in hub shell. 3 bearings in the 1-pc 6 pawl driver. Available in RHD and LHD options. Also sold as a complete wheel.