K18 LEAVE-IN MOLECULAR REPAIR HAIR MASK. NIB. A leave-in treatment mask that works on the molecular level to reverse hair damage in just 4 minutes. The K18PEPTIDE™ is clinically proven to repair damage from bleach + color, chemical services and heat* – with immediate and lasting results to restore strength, softness, smoothness and bounce to hair. Shampoo, do not condition. Towel-dry thoroughly. Begin with 1 pump and add more as needed. Maximum recommended usage is 3 pumps. Apply all over, 1 pump at a time. Let sit for 4 minutes. Do not rinse out. Comb, add product + style as usual. Use for 4-6 washes, then as needed.