It is an optical colour perfector for the nails thanks to a specific optical azurant that react to UV light. Used as a base under a nail polish, it restores its true shade : no more colour that turns into a dirty beige, a dubious yellow or a dull red ! Applied on non yellowed, non stained nails, it will give an original bluish effect. As it dries it becomes matt and so also suits men whose nails have been stained or yellowed, perhaps due to nicotine, and who are concerned about the apearance of their nails.