.7Z.001 File Extension

A 7Z.001 file is part 1 of a compressed archive created by 7-Zip, a free file compression and decompression utility. It contains one part of a multi-volume archive that splits a .7Z file into parts (other parts use the extensions ".7z.002," ".7z.003," and so on). 7Z.### files allow large 7Z archives to be broken into smaller parts for piecewise download or storage on external media with fixed capacities.

You need all parts of a 7-Zip split archive in order for 7-Zip to rebuild the original ".7z" file. Once 7-Zip has reconstructed the 7Z file, it can then decompress the 7Z file to extract the files from the compressed archive.

NOTE: Place all parts of a split archive in the same folder before attempting to rebuild the archive.