BUY THE BEST HAIR THICKENING PRODUCTS Hair fibers are products that are specifically meant for those people who are suffering from hair loss. They are powders or sprays that you apply directly onto your scalp, especially in the areas with bald spots. The material used to make these concealers and fibers resemble the biological components that make up your hair. Once you apply them to your hair, they stick to the natural hair in your head and covers the bald spot that had manifested in your head.