Western Digital builds 5mm-thick hybrid hard drive, Ultrabook makers sign on early
 

Those 7mm-thick hard drives you've seen in some Ultrabooks are already looking a tad on the chunky side. Western Digital has started producing sample versions of a hybrid hard drive (you're not yet looking at it here) that measures just 5mm (0.2in) tall, even as it crams in both flash and a 500GB main disk. If you think the slimmer drive is just the ticket for a best-of-all-worlds laptop that's both fast and capacious, you're not alone: Acer and ASUS have mentioned their collaboration in the same breath, which may be a strong clue as to where future Aspires and Zenbooks are going. The remaining question is when they arrive. Sampling isn't the same as mass production, which could leave us with months to go before the 5mm drive lands in future extra-skinny PCs.

http://www.engadget.com/2012/09/10/w...id-hard-drive/