: To open the file, place all parts in the same folder. Opening the first file (usually labeled .part01.rar or just .rar ) with a tool like WinRAR or 7-Zip will automatically pull data from the other pieces, including the 12th one, to recreate the original large file.

: You generally cannot use "Part 12" on its own. You need every preceding part (Part 1 through Part 11) and any subsequent parts for the file to be functional.

If you are trying to "provide a piece" or assemble this file, you must treat it as part of a larger set:

: Ensure all pieces are exactly the same size, as split archives usually distribute data in equal chunks, except for the very last piece.

: This is a proprietary archive format used for data compression. How to Use a Split RAR Archive