Acidic Bonding Shampoo is Step 2of Redken's most concentrated system ever. This sulfate-free shampoo provides an all in one solution to address all types of hair damage, even the most processed hair. A little goes a long way! This product is ultra-rich and thick in consistency and will coat your hair with less product than your average shampoo. We recommend you start with a quarter size amount and increase from there based on your hair type.