Western Digital is working on 5mm thick hybrid drives

Western Digital working on reducing the size of the disks. WD hopes to offer 500GB drives soon that are just 5mm thick. In 2008, a 9.5mm enclosure was required
 to harbor such a capacity, a number which dropped down to 7mm just last year.
                        Western digital has added 32GB of flash memory to the 500GB hard drive. The result is a hybrid disk called WD Black SSDHD. The WD Black SSD has a
downside as well. To use the available storage, special drivers are required for Windows operating system. Western Digital has not yet issued a statement on how this
will affect the installation and ease of use. The 5mm thick drive will have a special SATA-connector which will be featured only on specific ultrabooks.
        the exact released hasn't been mentioned yet.