Let’s connect with our life and image what’s the fiber of the fabric looks like? The same designed T-shirt, which has a different thickness. Generally speaking, D is a reference to the thickness of backpacks. From the appearance, the bigger D, the thicker silk, the thicker backpack; While the smaller D, the lighter silk, so the backpack is lighter, thinner. For example, a 210D fabric, which has a very fine organization, and generally used as the lining or layer of the backpacks. And fabrics with 900D or 1000D are thicker, abrasion-resistant, more suitable for the bottom of the backpacks.