Ten gears machined from a single block of steel. That's the construction approach SRAM takes with the XS-1299 XX SL Eagle T-Type cassette, and it's where the weight savings come from. The remaining two cogs—the 10-tooth and largest climbing gear—attach separately, but that monolithic middle section eliminates individual carrier spiders and the fasteners that hold traditional cassettes together.

The T-Type designation matters here. This cassette mounts directly to SRAM's XD driver body using a single lockring, but it's engineered specifically for the T-Type Transmission ecosystem. The tooth profiles and shift ramps are optimized for the Eagle T-Type derailleur's synchronized movement patterns. You can physically install it on any XD freehub, but pairing it with a non-T-Type derailleur defeats the engineering purpose and compromises shift quality.

The 10-52 range delivers a 520% gear spread. That 52-tooth bailout gear handles the steep pitches where traction matters more than cadence, while the tight spacing through the middle gears keeps your legs in a productive power band during sustained efforts. Nine and ten-tooth small cogs require the XD driver interface—standard Shimano HG freehubs won't work.... Read More