Sapphire Nail File.
Useful Tip: If you have hard or brittle nails, first soak hands in warm water (with Vitry Fizzing Nail Spa Tablets). File upwards towards fingertips and avoid shaping the corners of the nails. Use Vitry Nail Repair Care (Original, Matte or Sensitive) as a base coat or as a treatment to fix damaged nails.
Never had a diamond file before...love it!