In file sharing, large archives are often split into smaller "volumes." A file named 121.rar could be the 121st part of a massive multi-volume set. Safety and File Handling
Many aviation professionals use RAR files to store or share large sets of documents related to Federal Aviation Administration (FAA) Part 121 , which covers regularly scheduled commercial air carriers. These archives often contain training manuals, safety programs, or hazardous materials guidance. 121.rar
If you have encountered a file specifically named 121.rar from an unknown source: In file sharing, large archives are often split