Waterproof materialDouble waterproof and moisture-proof sealing on the surface and inner layer Scalable main warehouseZipper style expansion can store more items Back luggage strapMore convenient to carry while reducing weight Large capacity storageLarge capacity storage main compartment to accommodate more items Independent computer compartmentThickened protective computer compartment for greater security Back ventilation systemSoft and breathable, comfortable and not stuffy Stylish and practical, accompany you on every adventure. Easily handle your various outdoor explorations, urban commuting, and business trips.Zipper style expansion 5L Gently expand by 50mm, from 25L to 30LUSB charging design, plug and play for incoming calls To use this charging function, you need to bring your own power bank and connect it to the port inside the package.Back strap, can be used in conjunction with a suitcase Hand over the weight to the suitcase, which is stable and not easy to shake off Large capacity storage of various items to meet your daily travel needs For example: books, clothes, water bottles, umbrellas