SRAM XG999 Cassette

XX technology for 9-speed drivetrains

SRAM brings the XX group’s innovative X-Dome cassette to the 9-speed level with the introduction of a new XG999 cassette, set for release in mid-March.


Like the XX cassette, all but the innermost and outermost cogs on the XG999 model will be milled into a lightweight, dome-like shape from a single chunk of chromoly steel. Additional ports machined in between the cogs to allow mud and debris to pass through.  Sealing the large end of the ‘dome’ is a replaceable press-fit aluminum cog while the smallest cog will be a steel bit as usual. 

Not surprisingly, the XG999 cassette will be very light. It has a claimed weight of just 175 grams for an 11-32-tooth size —cleaving a full 100g from SRAM’s own PG-990 cassette and about 50g from a comparable Shimano XTR unit — while also promising better durability, too, on account of the harder steel cog material.

Prospective buyers should note that SRAM initially won’t offer the XG999 in the more versatile 11-34T size and pricing is set at a spendy US$300 — nearly three times higher than the PG-990.

Perhaps more interesting than the new cassette announcement is what this likely means for SRAM’s road groups, in particular the current Red flagship.  Red’s PowerDome cassette, the forebear of X-Dome, was a radical departure from conventional cassette construction but also criticized for its greater-than-average noise levels and susceptibility to clogging with mud in cyclocross applications. 

With the introduction of this new XG999, it’s now practically a foregone conclusion that we’ll see similar changes to the PowerDome cassette and even SRAM’s own road US road PR and media manager Michael Zellman tacitly acknowledges as such. 


“Our best technologies consistently find their way across our product platforms,” he said.  “This includes road to MTB, and vice-versa.”