Storage capacity and speeds One single-layer Blu-ray Disc (BD) can hold about 25 GB
or over two hours of HD video plus audio, and the dual-layer disc can hold approximately 50 GB. The data transfer rate is 36 Mbit/s
(54 Mbit/s for BD-ROM), but 2x speed prototypes with a 72 Mbit/s transfer rate are now in development. The BD-RE (rewritable) standard is now available, to be followed by the BD-R (recordable) and BD-ROM
formats in mid-2004, as part of version 2.0 of the Blu-ray specifications. BD-ROM pre-recorded media are to be available by late 2005
. Blu-ray Discs with capacities of 100 GB and 200 GB are currently being researched, with these capacities achieved by using four and eight layers respectively. On May 19
announced a prototype four-layer 100 GB Blu-ray disc.