Toppik Hair Building Fibers, made of colored keratin protein, blend undetectably with existing hair strands to instantly create the appearance of naturally thick, full hair. Instantly fills in thinning areas. Conceals hair loss. Makes fine hair look completely thick and full. Great as a root touch-up between colorings. Toppik Hair Fibers resist wind, rain, and perspiration for long-lasting results in all conditions.