K18 Leave-In Molecular Repair Mask 50ml 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. For best results, use for the first 4-6 consecutive washes following a service, and then every 3-4 washes as needed to maintain hair strength.