No. 4 Bond Maintenance Shampoo by Olaplex. Reparative shampoo for damaged or chemically treated hair. Olaplex presents the continuation of its iconic professional treatment with two steps to restore hair from home. It is a shampoo and conditioner that completes the use of steps 1 and 2 (professional, in the salon) and 3 (maintenance at home). This shampoo is suitable for all hair types and textures. Formulated with the brand's patented bond multiplier: the active ingredient bis-aminopropyl diglycol dimaleate. This component works by bonding to the sulfur and disulfide bonds of hair keratin, which break when subjected to aggressive treatments that alter its shape or color. It provides daily hydration without adding weight, repairs split or damaged ends, strengthens hair with every use, restores flexibility and manageability by softening and adding shine to the fiber. Vegan and respectful formula, without parabens, sulfates, or gluten. Cruelty-free.