The Shimano M771 XT 10 Speed Cassette is a high performance 10 speed dyna-system cassette. The hyperglide sprockets have a computer designed tooth configuration with contoured shift gates, resulting in a crisp smooth shift even under load. Close ratio gearing allows a more efficient use of energy through fine cadence control. The six largest sprockets are mounted on lightweight alloy carriers to reduce weight & increase rigidity. Sprockets are cut away & drilled to further reduce weight without reducing rigidity while the chrome-plated finish offers hard wearing resistance to corrosion. Designed for 10 speed HG-X MTB chains.