Lowest Price Salsa 12 mm Thru x 142 mm Shimano/SRAM 8/9/10; Shimano Dynasys 11 Bicycle Rear Hubs
About Salsa - "At Salsa, we believe a sense of adventure makes life better. The bicycle can be so much more than just a bike; it's a path to new places, new people, and amazing experiences."
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.