A duffel bag or kit bag is a large bag made of either natural or synthetic fabric (typically canvas), historically with a top closure using a drawstring. Generally a duffel bag is used by non-commissioned personnel in the military, and for travel, sports and recreation by civilians. When used by sailors or marines a duffel is known as a seabag. A duffel's open structure and lack of rigidity makes it adaptable to carrying sports gear and similar bulky objects.

A duffel bag is often confused with a hoop-handled hard-bottomed zippered bag, known generically as a gym bag.

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