Shimano XT 9 Speed Cassette CS-M770
Trickle down technology from XTR gives this cassette the same engineering using less advanced(read - less expensive) materials. Top six cogs reside on an alloy carrier which greatly reduces stress on the hub, stiffens the cassette for better shifting and saves weight to boot. Albeit a bit heavier than the XTR cassette, the value cannot be denied at less than half the price. For this reason, many XTR fans will run XT cassettes - this is probably the first component that gets replaced in an XTR group.
Durable chrome-plated steel cogs have great wear time and clean up well. They also provide perfect glide while shifting. The proven Hyperglide tooth profiling is a proven winner.