Hitachi GST is announcing the Travelstar Z7K500 today, a 2.5-inch hard disk that it claims is an "industry first." The drive is just 7mm high, runs at 7,200RPM, and fits 500GB onto a single platter. On top of this, Hitachi says that it's the first 7mm-high 2.5-inch drive to include a 6Gbps SATA interface and 32MB cache. Hitachi is aiming the Z7K500 squarely at the ultrabook market, arguing that the thin and light size combined with better economy per GB make it good competition for SSD-only solutions. The drive began shipping to manufacturers for testing in January, while high-volume shipments are set to begin in March.