BosleyMD BosVolumize Hair Thickening FibersCreate Thicker, Fuller Looking Hair. BosVolumize Hair Thickening Fibers naturally bond to existing hair with keratin fibers that blend and cover thinning and low density areas. Because our own hair is made of Keratin and naturally holds a positive charge, BosleyMD Hair Thickening Fibers are designed to mimic our own human hair but with a negative charge. Therefore, when negatively charged, lightweight, easily blended BosleyMD Fibers come in contact