A highly-nourishing and reparative shampoo that leaves hair easier to manage, shinier and healthier with each use. It repairs and protects hair from everyday stresses — including damaged hair, split ends, and frizz — by re-linking broken bonds. N°4 is color-safe and proven to reduce breakage and strengthen all types of hair. PH Balance: 6-6.5 How to Use 1. Apply and massage product throughout hair. 2. Rinse product from hair. 3. Follow with Olaplex N°5 Bond Maintenance Conditioner (sold separately).