Pros: It keeps the chain attached to the drive train.

Cons: It's needlessly heavy and comes stock on WAY too many bikes. It's the worst part of OEM parts specs.

Recommendation: Buy an XT 9 speed cassette.

Pros: Very strong cassette in general, has a larger range of gear ratios than the PG-950, ease of mounting, and fluent shifting throughout the cogs.

Cons: None

Recommendation: I have been rolling with this cassette for several years when I am trail riding through big hit gravity riding. It has worked flawlessly with fluent shifting throughout the cogs. When I am doing big DH runs, I will mount the DH cassette. This cassette has offered great service over the years and I am very pleased with Srams line of cassettes.