Many users of Olaplex No. 4 Shampoo report noticeable improvements in the texture, strength, and appearance of their hair, especially when used in conjunction with other Olaplex products in the Bond Maintenance system, such as the No. 3 Hair Perfector and No. 5 Conditioner. Overall, Olaplex No. 4 Shampoo is highly praised for its ability to help restore and maintain healthy, vibrant hair.