Bosley Hair Thickening Fibers are a safe and effective way to eliminate the appearance of baldness and thinning hair. It is perfect for both men and women with hair loss, as well as recent hair transplant patients. They are available in a variety of hair colors: black, dark brown, medium brown, light brown. BosVolumize Hair Thickening Fibers provide instant thicker fuller-looking hair. Blend and cover thinning and low-density areas with Keratin Hair Fibers that naturally bond to existing hair for instantly thicker, fuller-looking hair. Also great as a root touch up between color service.