A double-sided, dual layer pre-recorded DVD disc format, with a capacity of 17.1 GB (approx. 8 hours) currently used for a very small percentage of discs available.
DVD-18 is a double sided dual layer DVD which can fit up to 17 GB or 15.9 computer GB which some commercial video DVDs are using today (a DVD-18 is basicly four pressed plastic DVD-5s pressed together, they are not burned). Video DVD supports this format but DVD-R/W and DVD+R/W does not support this format.
A DVD disc with two data layers on each side, giving a raw storage capacity of about 15.9 gigabytes.