Six cogs mounted on two aluminum spider arms, four individual steel cogs on the small end, and a construction robust enough that Shimano has kept it in the catalog through multiple XT generations. The CS-M771 is the 10-speed cassette that sits behind Dyna-Sys drivetrains — closer ratios than the old 9-speed platform, HG-X chain compatibility, and shift ramps machined to work with the M770/M780 XT rear derailleurs. It's the workhorse choice for anyone still running 10-speed, whether that's an original build being maintained or a wheel swap that needs to match an existing drivetrain.

Three gearing options cover the range of 10-speed mountain use. The 11-32T is the tightest option with single-tooth jumps through the smaller cogs and a more road-like progression, which works well for XC riders or anyone running a 2x or 3x front setup where the front rings handle the big range shifts. The 11-34T adds one more tooth at the top for climbing without a huge gap penalty. The 11-36T opens things up further with a 32-36 jump at the low end — the pick for 1x conversions or riders who need bailout gearing on steep, sustained climbs.

The two-spider aluminum construction on the six largest cogs is where the XT designation earns its keep versus the SLX and Deore alternatives at the same speed count. The spiders keep weight down while providing a rigid platform that maintains cog spacing under climbing loads. The smaller four cogs are individual steel pieces that slide onto the freehub body separately, which means when you eventually wear out the most-used cogs, you can pull the cassette apart to inspect what needs replacing rather than tossing the whole thing.... Read More