The STDZ750100 model number has an unformatted capacity of 750GB but is the same size as the 500GB model that is already on sale.
Measuring 82 x 122.5 x 7mm, it is among the most compact 750GB hard drives on the market. Apparently they got it so thin by using the metallic cover of the drives as one of the sides. Insulating sheet metal is placed on the other side.
The drive supports USB 3.0 host interface. Since the drive is bus powered, meaning it draws power directly from the USB port, and does not require an external power supply, the Seagate Seven is designed for those on-the-go.
It's up on Amazon for $130 in the US. The 500GB model from Seagate currently retails for $99 in the US.