Make them easier to transfer over email or cloud services with file size limits.
Do you have the part of this archive, or are you trying to repair a set with a missing piece? 7z.001 7z.002 7z.003 help please - SourceForge
The file is the second part of a multi-volume 7-Zip compressed archive. On its own, this file is just a "piece" of a larger dataset and cannot be opened or extracted without the other accompanying parts (at minimum, the first part ending in .001 ). How to use this "piece"