The back structure of the double shoulder bag directly determines the use and grade of the backpack. Brand-name computer double shoulder bag structure of the back is more complex, at least six pieces of EPE or Eva to do through the air cushion, and even aluminum racks. The general shoulder bag back is a 3MM or so of pearl cotton to do breathable plate, the simplest bundle pocket type shoulder bag in addition to the backpack itself, there is no liner material. The computer double shoulder bag quality is good, but the style is few. Sport double shoulder Bag style choice more, but the material workmanship general. The stylish backpack is small in size but suitable for use by ladies in informal settings.