The current generation of ultrabooks is powered by 7 mm hard drives but this can change soon thanks to the efforts of both Intel and Seagate.
Some time ago Intel was the company to specify future 5 mm hard drives, which have the capability to provide enough capacity at a low enough cost. Hard drive makers so far have not picked up the idea since the standard storage solution for ultrabooks is a hybrid SSD/hard drive device but now it seems Seagate will be the first company to debut a 5 mm hard disk drive.
There are, of course, a few problems that Seagate will have to resolve – stabilization of the recording and reading process as well as some cost issues. The first 5 mm ultrabook hard drives are still expected some time in 2013.
Source: Overclockers.ru