cassette

The cassette is the group of sprockets on the rear wheel of a bicycle. It consists of several individual sprockets (also called pinions) that are pushed onto the freewheel body of the rear hub. The cassette is a central component of the drivetrain and works directly with the chain and derailleur.

Depending on the bike type and intended use, a cassette can have between 7 and 13 sprockets , with modern road bikes and mountain bikes often using 11- or 12-speed cassettes. The different sprocket sizes allow for different gear ratios — for light gears when climbing and heavy gears for flat or fast terrain.

The cassette is driven by the chain when you pedal, transferring power to the rear wheel. When you shift gears, the rear derailleur moves the chain from one sprocket to the other. For smooth operation, it's important that the cassette, chain, and rear derailleur are all coordinated.

👉 Note: The cassette is not to be confused with the screw ring, which is used on older bicycles and has a different mounting system.