SRAM 12 mm Thru x 142 mm Shimano/SRAM 11 Speed Road Bicycle Rear Hubs
About SRAM - "Incremental enhancements. Perpetual improvements. Revolutionary Innovation. When advancements are continuously made to every attribute of every component, the result is overall performance that is simply second to none. And to real cycling enthusiasts, there is nothing more gratifying then achieving the ultimate ride. And the best part is we just keep making it better. This is what SRAM is all about."
This is hub spacing and is the width of the hub. It must match your frame specifications.
The cassette body type is the type of cassette and number of speeds the hub will accept.