Sprockets, cogs and cassettes at cheap prices from starbike.com, the bicycle online shop
A cassette (also called rear sprockets) is mounted on a freehub of a rear hub and consists of 7 to 11 individual cogs. In combination with the rear derailleur it is responsible for the selected (rear) gear.
Cheaper cassettes are riveted together completely, while today's high performance cassettes consists of partially individual cogs (an example are Shimano XT cassettes), which lowers the weight and makes the replacement of worn out cogs easier.
The cassette is being fixated with a lock ring on the freehub shell of the rear hub. There are two different standards of freehub shells: the Shimano HG standard (which SRAM uses as well) and the Campagnolo ED standard. This needs to be considered before buying, because Shimano and Campagnolo cassettes are not compatible to each other. The freehub type is listed in the product name of all hubs and wheels.
If you're unsure which cassette is the right for you, contact us and we'll help you.