In terms of material, one kind of fabric isn't better than another as long as the fabric is washable and breathable. Mora recommends flannel as a good option in addition to cotton and quilting materials. The World Health Organization recommends looking for masks that have a white or light colored interior, which can help you see when the mask is dirty or wet. The WHO also recommends finding a mask in which the outermost layer is made from a hydrophobic material, such as polyester or a cotton and polyester blend, that will help repel droplets and moisture. more