Because backpacks are used in special environments, high requirements are put forward for the materials and processes of backpacks. All the stress positions of the backpack are stitched three times with stitches to make the stressed positions strong and durable. The buckles and other parts of the backpack can be used to prevent freezing, smashing and deformation at 120 degrees Celsius without damage. THE EXTERNAL MATERIALS OF THE BACKPACK MAINLY INCLUDE 420D OXFORD NYLON, 1000D NYLON, 600D OR 1000D POLYESTER (POLYESTER), OR 1000D CORDURA AND OTHER MATERIALS. 1000D material has high density, is very wear-resistant, and is very suitable for use in the field. CORDURA is a well-known high-grade wear-resistant nylon roving fabric developed by DuPont in the United States. The wear resistance of the material is much higher than that of ordinary nylon or polyester, and it is lightweight. More than 90% of the world's famous brands of backpacks use this prestigious nylon material. These materials can withstand a water pressure of 0.5m~2m, so that the objects in the bag are kept dry. Some materials also have a rip-proof function, and once punctured, the breach will not tear and expand.