Today we are going to look at the Hitachi 5K500.B 2.5-inch HDD for notebook computers. The drive is only 9.5mm thick and needs only 1.4W during read/write operations.
One of the most common upgrades that power users perform on their notebooks is adding a larger hard drive. The hard drive is high in capacity with 500GB of storage space, but offers some of the lowest power requirements in the industry.

http://www.i4u.com/section-viewarticle-527.html