K18 Leave-In Molecular Repair Mask 5ml is a patented bioactive peptide treatment that strengthens and improves elasticity while reversing damage from chemical services, thermal styling, and mechanical styling for all hair types. This leave-in mask heals and strengthens hair with lightweight moisturizing benefits to detangle and keep hair smooth and soft, without weighing it down. The 5mL starter size is a 2-application dose for most hair types, and for best results, use on consecutive washes.