K18 molecular leave in repair maskA leave in hair treatment to reverse chemical and physical damage to hair. We tend to put our hair through a lot, which is where the K18 Leave In Molecular Repair Mask comes into play. This no rinse hair treatment, made with a patented bioactive peptide, promises to reverse damage caused by colouring, heat and styling. Think of it as an apology note to your frazzled, stressed out hair one that works by repairing the keratin within each strand. You can