Large textures or "re-baked" (REB) game files.
Select "Extract Here" or "Extract to Reb1MF/". The software will automatically pull data from the other parts to recreate the original file. Safety Note
The .001 extension indicates this is the "header" or beginning of the sequence.
Right-click on the .001 file specifically.
Ensure you have every numbered file in the sequence (Reb1MF.7z.001, Reb1MF.7z.002, etc.) saved in the same directory.
If you did not expect to receive this file or downloaded it from an unverified source, exercise caution. Split archives are sometimes used to bypass email or browser file-size limits, but they can also be used to hide malicious executables from basic scanners.