Bosley's Bosvolumize Hair Thickening Fibers are a keratin-based hair loss concealer that adds volume and thickness to thinning hair. The fibers are designed to blend with your existing hair for a natural look.Keratin fibers: These fibers thicken the appearance of hair by clinging to existing strands. Botanical extracts: These may nourish the scalp and promote hair growth, although the effect is likely limited. Easy to use: The fibers are applied with a shaker and blend into hair. Bosvolumize Hair Thickening Fibers may be a good option for people with thinning hair who want to create the appearance of thicker hair. However, it is important to note that these fibers are a cosmetic solution and do not treat the underlying cause of hair loss.