Dual Layer Media (DVD-R DL) or Double Layer Media (DVD+R DL) (called by the RW Alliance), means that much like commercially pressed DVD-ROMs, these recordable discs have two layers of dye, almost doubling the size of older DVD5 format to 8.5GB. This is a recordable DVD9 format.
Note that not all DVD burners have the ability to record in the Double/Dual Layer format. If you are shopping for a DVD burner that supports this format, make sure that it is explicitly stated. If your currently own a DVD burner does not have this capability, it is possible to be upgraded to burn Double/Dual Layer media via a firmware update. Please check with your DVD burner manufacturer for additional details.
){kind=link}