She shows off enviable, HEALTHY AND PRETTY nails. Fragile Nail Treatment. The DUO Sora HARDENING Treatment strengthens the nail and provides necessary vitamin elements for an ideal shine and protection. Its keratin content normalizes the growth of the nail. REGENERATING VARNISH hardens the nail, strengthens it and provides vitamin elements, providing shine and protection. Combined with the GREEN HARDENER, we will get healthy and beautiful nails. It can be used as a base prior to lacquer.