Attention should be paid when purchasing bags molded by EVA molding machines. The bag has a legitimate trademark, factory name, address, and certificate of conformity. Generally, good bags are made of sturdy steel with iron pendants, rather than iron sheets and wires to fill your inventory. If it's the type of backpack, the EVA molding machine uses several layers of canvas to form all the stressed parts, and it is tightly rolled with a sewing machine. The straps are wide and there is a large shoulder pad at the joint with the shoulders. When purchasing an EVA bag, it is also important to carefully observe whether there are any skipped stitches, missing seams, or the density of the needle and thread inside the bag.