Light, stiff and durable, this 10-speed cassette is designed to cut down shift times and help improve shifting performance, even during bad trail conditions and under load. Three largest cogs are mounted on a lightweight alloy carrier to reduce weight and increase stiffness Cogs are milled and drilled to reduce weight even further Special computer-designed tooth configuration with contoured shift gates for precise, smooth shifting, even under load Close-ratio gearing lets you fine-tune your cadence for optimum performance Compatible with super-narrow 10-speed Hyper Glide chains only