 Blu-ray Discs contain their data relatively close to the surface (less than 0.1 mm) which combined with the smaller spot size presents a problem when the surface is scratched as data would be destroyed.To overcome this, TDK, Sony, and Panasonic each have developed a proprietary scratch resistant surface coating.TDK trademarked theirs as Durabis, which has withstood direct abrasion by steel wool and marring with markers in tests.