Design space: Expandable carry-on luggage Product: Dror for Tumi International Expandable Carry-On Design: Dror Benshetrit Territory: Worldwide American luggage brand Tumi wanted to introduce hand luggage that would be rigid enough to protect the contents but that could also increase in size. This would help travellers who want to carry different amounts of luggage, sometimes in one trip. Some expandable cases increase their capacity by unzipping a fabric panel. But Tumi wanted the shell to remain rigid in order to protect the contents. New York-based designer Dror Benshetrit created a hard case that is small enough to be classified as hand luggage, but can be expanded into a large but rigid, case by using an internal telescopic wall system that increases its depth. The inside walls of the polycarbonate shell are lined with two spring-loaded panels nestled together. To expand the case, the user presses down on the inside base with one hand, and pulls on two internal straps with the other. This releases the panels upwards to increase the size. Pulling on a second pair of straps brings one of the panels up again. The function is similar to a retractable telescope. The depth of the case, which sells for $895 (£895 in the UK), increases from 9in to 18in. In carry-on mode, the bag has a capacity of 31.3 litres. This increases to 46.1l in its first expansion, and to 61.4l at its second.