Nutra Nail Mineral Nail Care Rock Hardener .5 fl oz (15 ml) (Nagelreparatur) - Nutra Nail Mineral Care Collections Rock Hardener supports nails and prevents future damage. - It is acrylic hardening formula plus Minerals and Forms a break-resistant shield. - Nutra Nail has added Copper, Magnesium and Silica, essentials from nature, to this unique hardening formula that brushes on clear. - Nails are sealed for added protection from chipping, cracking and splitting. And the beautiful finish lasts and lasts! Get hard.