It sounds like a Zen koan.What gets bigger as it becomes smaller? The answer to this riddle, though, is hardly metaphysical: it is portable storage devices, which began with 5.25-inch floppies that held a paltry 1.2 megabytes of data and have evolved into USB flash drives that are smaller than a stick of chewing gum yet can hold several gigabytes of data.

A new portable storage device called Outbacker by Memory Expert International (MXI) is a bit bigger than a flash drive—it’s about the size of a deck of cards—but it makes up for its size with an incredible 20 GB of storage space (a model with twice as much storage is also available).

It offers several security features that make the device a handy tool for anyone who needs to bring along every file that could possibly be needed without fear that confidential information will be lost if the unit is stolen. For example, unlike a typical USB drive, the Outbacker cannot be read by the computer you plug it into until you press a preregistered finger on the unit’s tiny reader. Once you do, a light on the unit switches to green and the Outbacker becomes available for use.

Files moved to the Outbacker can be encrypted for added security, and a feature called MXI Private Disk provides an area on the device that can be additionally secured via password (there can be multiple private disks on each Outbacker, so several users can share one device). Transferring a large number of files takes a bit of time—in my test it took about five minutes for a 267 MB folder with close to 1,700 files in it—but that’s to be expected.

Two types of users—administrators and general users—can be registered on each device. The administrator account is used to manage the users, set security policies, and enroll user fingerprints.

The device comes with a leather pouch that can be clipped to a belt. Also included are two cables, a cloth to clean the fingerprint scanner, and a power cord (the Outbacker is normally powered through the USB connection, but not all computers will provide enough power to run it). Thick rubber corners keep the Outbacker safe from casual falls.

Pros. The Outbacker is handy to carry around and simple to use. The fingerprint scanner worked flawlessly.

Cons. It’s costly—$499.99 for the 20 GB model, $659.99 for the 40 GB model.