Reliable, perfect shifting awaits with Shimano's Deore XT Dyna – Sys Cassette. It features chrome – plated steel sprockets mounted to two aluminum carriers for an ideal blend of durability and low weight. Closer gear ratios in the middle of the cassette ensure you'll have the perfect gear for the trail's ups and downs. Plus, the cogs are ramped and machined for flawless, lightning – fast shifts.