The 500GB WD My Passport Edge weighs just 130g despite an all-aluminium case.
And to match the current trend in notebooks, it's only 11mm thick, 112mm long and 83mm long.
The Edge is available preformatted as HFS+ for Mac, or NTFS for Windows.
It can be used with OS X's Time Machine backup feature, or the included WD SmartWare backup software for Windows.
A USB 3.0 interface is provided for speed (up to 5Gbps, according to company officials), but as usual the drive can also be used with a USB 2.0 port if that is all that is available on the computer. The Edge is bus powered.
"We know that people who bring personal and business content along with them on their travels are concerned with portability and with maintaining privacy while also protecting their data.
"We design all My Passport products with a small footprint and with security and protection in mind."
The drive costs $129 for either version - unless you're in New Zealand where the prices are $NZ169 for the Windows version and $NZ189 for the Mac version (go figure).