Replace a worn driveshell or one that got notched up by a loose cassette. These will work with 8, 9 and 10 speed cassettes.
The body is perfectly machined from aluminum billet. Inside of the drive shell are pre-installed Chris King bearings, which makes installation a breeze.
A little spendy, but worth it. Does not work on ISO hubs though.
Pros: Light, functional,