Look Thick Hair fibers are tiny static-charged strands made from keratin. Also known as hair building fibers, these sprays and powders work quickly to fill in thinning hair, patchy beard and cover bald spots. It is the best hair building fibers look identical to an individual’s natural hair no matter if it’s straight or curly. You can easily use hair fibers on your own at home. While you can follow the instructions on these products.