: WinRAR (the original developer of the format) or 7-Zip (a popular free, open-source alternative).
Splitting archives was common for fitting data onto multiple CDs or DVDs, but it is still used today to: Download r21 rar
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. : WinRAR (the original developer of the format)