The top five cogs are grouped as three and two, respectively, and are riveted to anodized aluminum spiders that add stiffness to improve shifting. The remaining six cogs are individual with spacers between, and an anodized aluminum lockring screws into the freehub to hold the entire assembly together. One spline of the cassette is wider than the others and corresponds with the splines on the freehub, so the cassette cogs can only be installed with the right clocking of the shifting ramps, timing them for perfect chain pick-up and release. This innovation is true to Shimano's Japanese culture, which uses the term "poka-yoke" to refer to features—like these guiding splines—that serve as built-in wards against user error.
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