Hard coating can enhance lenses’ anti-scratch and anti-rfiction abilities. Lenses are being rubbed and cleaned frequently for years. A stronger anti-friction ability ensures you lenses to be more endurance and thus a longer life span .The hard coat also makes other coatings such as mirror coating more adhesive to the lens. It also preserves the tint of the lenses. Our hard coated CR39 lenses can pass the Drop Ball Test easily.