Toppik's Medium Brown Hair Building Fibers are created with high-quality keratin protein. Medium Brown hair building fibers appear as a warm shade between lightest and darkest brown. They work best on individuals with medium brown hair. They magnetically attach to the natural hair strands for a thicker outlook. These fibers also feature Toppik's newest technology that allows them to resist wind and moisture. It is a useful product for individuals looking to make their thinner hair appear fuller.