Besides being the safest backpack it is also the most convenient backpack Internal structure: pocket computer package Open cover: zipper Material: Canvas Color: light gray, dark blue, black, army green, red Size: 14 inches 46*31*14cm Note: There is no mobile power comes with the backpack inside. If you want to use External USB Charge Function, you have to do as follows: 1.Buy a mobile power 2.Connect your mobile power with the USB interface inside the backpack 3.Connect your phone with the USB interface outside the backpack 4.Charging begins. There are 2 kinds of mobile power in the market. 1:Plug in your phone, you can start charging 2:Plug in your phone also need to press button of mobile power then start charging To cope with this backpack, we suggest purchase of the first mobile power.