While "REV_felek" is a specific naming convention, "REV" often stands for "Revision" or is a tag used by specific release groups in the emulation or gaming scenes. If this is a software update, ensure you are applying it to the correct base version of the program.
In most multi-part sets, all parts except the very last one will be exactly the same size. If part6 is significantly smaller than the others, that is normal—it simply contains the remaining "tail" of the data. Extracting the Data Place all parts in the same folder. Right-click on Part 1 (not Part 6). Select "Extract Here" or "Extract to REV_felek/" . REV_felek.part6.rar
: This usually means one of the parts (like your Part 6) was corrupted during download. You may need to redownload that specific part. While "REV_felek" is a specific naming convention, "REV"