This file set by 95 & Sunny is Czech Republic made tempered glass. They are guaranteed to never wear out or wear down. They can be use on natural or artificial nails. Continued use reduces chipping, peeling and splitting of natural nails. Won"t tear or harm delicate skin - safe for diabetics and babies. Filing surface is non-porous, double-sided and permanently etched into the glass. Board certified in every state for manicurists. Made from float glass, the same process used to produce wine goblets and crystal vases. Environmentally friendly - NO LEAD is added or chemicals used during the manufacturing process. Tempered and hardened for durability and safety, 102% stronger than standard glass. Each file comes with a protective sheath.