Most expandable luggage has a zipper around the perimeter that, when unzipped, releases more cloth to provides an inch or so extra storage room.  The new Zipsak Boost from Biaggi reaches new highs —  and lows — in variable packing space.

The 15-inch by 10-inch by 5-inch nylon pouch unzips to become a 22-inch by 14-inch by 9-inch-deep carry-on and even further to a 28-inch check-through suitcase.
The 15-inch by 10-inch by 5-inch nylon pouch unzips to become a 22-inch by 14-inch by 9-inch-deep carry-on and even further to a 28-inch check-through suitcase.

What starts out as a stashable 15-inch by 10-inch by 5-inch-deep crinkle nylon pouch, unzips to become a durable 22-inch by 14-inch by 9-inch-deep carry-on – with four 360-degree spinner wheels, double adjustable pull straps, carry handles on the side and top, two exterior zippered pockets, and an interior mesh compartment.

Dual zippered openings let you pack from the top or with the bag lying horizontal. But wait, there's more —  6 inches more. Unzip the wrap-around zipper just above the wheels, and the Boost lengthens to a 28-inch check-through suitcase. Reverse the process and the bag shrinks back to carry-on size or its pouch persona.

The Boost weighs in at less than 4 pounds, one of the lightest 4-wheelers on the market.

          Biaggi Zipsak Boost, in a choice of six colors, lists for $95, but is available at a substantial discount at biaggi.com.