spool

If you need to reload film, the cassette can be rewound slightly by turning the hub located on one end of its spool.

The high-pressure spool rotates faster than the intermediate- and low-pressure spools, as the high-pressure turbine is driven by superheated combustion gases straight out of the burners, while the high-pressure compressor has to spin very fast to compress air that has already been compressed and heated by the low- and intermediate-pressure compressors.