(1) The outer fabric of the two-in-one single-backpack is made of nylon Oxford cloth + PU fabric. This material has strong tensile strength and wear resistance. Its high textile density and water-repellent coating can effectively block Rain water soaks the bag, this combination has better waterproof performance, and has a noble luster. Waterproof performance can reach: IPX3 or IPX4 level. (2) The inner lining is made of 210D nylon Oxford cloth, which has a shiny texture. (3) The inner filling is made of high elastic EPE cotton. This material is lightweight, shock-resistant, and can effectively protect the contents of the bag. sling backpack