Full-Size Leave-In Molecular Repair Hair Mask is a salon-grade, leave-in treatment that repairs hair on a molecular level in just 4 minutes. Powered by the biotech-developed K18PEPTIDE™, the formula reconnects broken polypeptide chains (and, as a result, disulfide bonds) to restore strength, softness, smoothness and bounce—delivering immediate and progressive reparative results for damage caused by bleach & colour, chemical services and heat.