DVD-18 discs (Type D in ISO) effectively combines the DVD-9 and DVD-10 disc types by containing four recorded data layers (allocated as two sets of layers 0 and 1) such that only one layer set is accessible from either side of the disc. These discs provide a total nominal capacity of 17.0 GB, with 8.5 GB per side. This format was initially used for television series released on DVD (like the first releases of Miami Vice and Quantum Leap), but was eventually abandoned for single sided discs for reissues.