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 and increase rigidity sprockets are cut away and drilled to further reduce weight with