The Opti.smooth Revitalizing Smoothing System contains pro-keratin, to strengthen the hair fiber and help prevent breakage to ultimately provide 25% more conditioner. Pro-keratin is a complex of amino acids and proteins. This complex contains positively charged ingredients and is attracted to the negatively charged sites of damaged hair. Attaches to damaged sites, helping to treat and revitalize the hair. This leaves hair stronger and better protected throughout the service.