The cassette roll is made of a polyester type plastic film with a magnetic coating based on gamma ferric oxide (Fe2O3). It is magnetic so it can be pulled round and round the cassette wheels very easily without getting stuck or jammed.
The cassette cover or case is made out of Polyamide (Nylon). This is because this type of plastic has a good resistance to chemicals. Also it is a tough casing so the inside of the cassette doesn't get destroyed.
This part of the cassette is made of brass. It is made of that material because it is the part that holds the cassette together. They use brass because it is a lot stronger than most plastics.
Cassettes were the old fashioned form of CD's. There are still slots for them to fit in to most modern day radios because lots of people still want to use them. This cassette also comes with a hard plastic cover to protect the actual cassette from any damage that it could get when it is not inside the cassette player.
The small parts of the cassette are either made from Urea formaldehyde or Phenol formaldehyde. This is because these materials don't need to be strong and they are cheap to manufacture.
This part of the cassette is called the Mu magnetic shield. It was needed as a shield in older cassette players.
This is a thin piece of metal that is on either side of the cassette. It is made out of aluminium and is designed to help the magnetism of the cassette roll. Also it can act as another protecter for the inside of the cassette though it is not ideal to get it scratched.