The .r21 file extension is part of a . When a file is too large to be easily shared or stored on a single disk, developers use tools like WinRAR to "split" it into multiple volumes.
: You must always open the first file in the sequence (usually the one ending in .rar or .part01.rar ).
: Right-click the first file and select "Extract Here" or "Extract to [Folder Name]."