Thickening fibers that naturally bond to existing hair with keratin fibers to blend and cover thinning hair and low density areas. Thickening Fibers are designed to mimic our own human hair but with a negative charge. Therefore, when negatively-charged, lightweight, easily blended Bosley MD Fibers come in contact with our positively-charged hair, it creates a static-cling effect, naturally binding to the hair shaft creating instantly thicker, fuller looking hair.