.DUC File Extension

Saved game created by the Action Replay Max DS, a hardware device used to apply cheat codes to Nintendo DS and DS Lite handheld console games; saved in Action Replay Max DS's proprietary format, but can be converted to a traditional .SAV file and loaded with a Nintendo DS emulator.

The Shunyweb website can be used to convert DUC files to SAV files. You can also use the programs max2sc.exe and ARDStoSAV.exe.