The underlying compression format is 7-Zip, which uses high-ratio LZMA/LZMA2 algorithms .

The file is the fourth part of a split compressed archive created with the 7-Zip utility .

This indicates it is the 4th volume in a sequence. You cannot open this file independently; it is a "chunk" of data rather than a complete standalone file.

The software will automatically pull data from .004 and the other segments to reconstruct the original full-sized file.