Not all luggage is created equal. Even bags of a similar type vary tremendously from manufacturer to manufacturer, so when you're buying one you should always look closely at how it's made. Fiberglass inner frames ensure both strength and light weight. Inner structures may also be made of aluminum, wood, durable molded plastic compounds, or any combination of the above. A weighty frame will make a case heavy even before it's packed. Frame materials are often listed on the luggage tag; your luggage salesperson should also be able to tell you what they are. On cases with zippers, look for taped seams, in which a strip of cloth reinforces the zipper and bag connection; this prevents fraying. On the outside of the bag, joints should be covered with leather, nylon piping, welts to reinforce the seams and absorb wear and tear. Also, seams should be lockstitched -- a method in which each stitch is reinforced, or locked, to stay in place and stand alone. This way, if one stitch happens to break, it won't take the next one with it and unravel your seam. Fabric counts for a lot in luggage. Leather luggage can be very durable and looks marvelous, but it is often too heavy to be carried even when it's empty. Top-grain or full-grain leather, the outermost layer of the hide, is stronger and more durable than leather made from splits, the layers of hide that are split off from underneath the top grain. Luggage made from splits costs less but is more likely to show wear. Among the various fabrics available, those that are heavier protect the bag's contents better and stand up to sharp objects that might cause tears or rips in transit. Popular these days are ballistic nylon and Cordura nylon. Ballistic nylon is a bit more expensive but worth it. The same bag made of Cordura or Cordura Plus costs less and is still pretty sturdy. Although tweed and brocade bags may appear sturdier than nylon ones, they are slashable and the thicker fabric adds weight. There are some other unusual fabrics that are perfect for the traveler concerned about the environment. These include Fortrel EcoSpun, a durable material made from recycled plastic bottles, and fabric woven from hemp. Luggage from American Tourister, Kipling bags, and Travelpro bags are all good.