According to Digitimes, it appears that HDD makers have joined up forces in order to slim the 2.5-inch standard down to 5mm. This will allow HDDs to squeeze inside Intel's Ultrabook specification and give SSDs run for their money. Apparently, HDD makers are aiming for hybrid design in order to give it as much performance as possible.

Digitimes reports that the new 5mm thick HDDs are still in the planning stage and far from being manufactured so we are not going to see them anytime soon. According to Digitimes' sources, there are some issues and, in addition to the increased cost generated by this diet, a major one is stabilizing read and write actions.

Hybrid HDDs are apparently becoming a popular solution for ultrabook products and are expected to be a part of many mid-range and entry-level models in the future. The hybrid HDDs are expected to gain momentum in the Q1 2013.

As noted, 5mm HDDs are still a long way from showing up in various notebooks and ultrabooks. You can check out more here.