Apple does not provide macOS installers in the .RDR format. Official downloads are provided as installers or macOS High Sierra 10.13.5 Update
If "rdr exclusive" is important
Instead try:
The macOS High Sierra 10.13.5 RDR image is a powerful tool for system recovery and specialized installations. By following proper verification steps and using reliable imaging software, you can breathe new life into your Mac hardware with one of Apple's most stable legacy operating systems.