redken acidic bonding concentrate shampoo is redken's most concentrated all-in-one formula for strength repair for all types of damaged hair. this ultra-rich and luxurious sulfate-free shampoo provides ultimate strength repair, intense conditioning and color fade protection. featuring citric acid, this shampoo contains a concentrated bonding care complex that reinforces weakened bonds within your hair to improve hair strength and resiliency. this ph-balancing shampoo is specifically formulated with an acidic ph to defend against the negative effect of hair coloring, styling tools, and even water, which has a ph of 7, to balance hair's ph back into a healthy range of 4.5-5.5. the result? healthier looking and feeling hair.