Leave-In Molecular Repair Hair Mask K18 Repairs Even The Most Extreme Damage, Returning Hair To Its Younger, Healthier State. This Leave-In Mask Penetrates To The Innermost Layers Of The Hair, Increasing The Benefits Of Other Traditional Repair Products. Formulated With K18 Peptide, It Is Sized To Fit And Reconnect Broken Keratin Chains, Renewing Hair With Strength, Smoothness And Elasticity.