Just started using this serum on my hair. I am a true Redken customer and swear by their products but wanted to try something perhaps more intense since this summer I was subjected to hard well water which was causing havoc with my hair in terms of metal and mineral build up and damage. (I tried the shampoo too). I will continue to use to see how this product works long-term. So far it seems to really liven my hair making it softer more manageable and stronger.