Sling backpacks are a smaller backpack style that usually holds on an average 10 -20L, give or take a bit. Although it somewhat resembles a cross-body, it's a backpack for travel and other things. A longer strap goes over your head, or you can sling it over just one shoulder like a purse. Some have adjustable straps to fit different size torsos, while others have padded straps. It has a pyramid shape or an oblong rectangle shape except for flat in the front and back, and most conform to your body for comfort.