OLAPLEX No. 0 Intensive Bond Building Hair Treatment is a professional-inspired, intensive treatment that primes hair for deeper repair, strengthens, and protects hair integrity leveraging the OLAPLEX patented bond-building technology. It primes hair to intensify benefits of the No. 3 Hair Perfector, strengthens weakened bonds deep within the hair strand, and repairs hair from chemical, thermal, mechanical, and environmental damage..Suitable for all hair types.Scientifically proven 3x stronger & 68% more repair when used with No. 3 Bond Perfector.Vegan & cruelty-free.5.2 oz/ 155 ml.Apply No. 0 to dry hair, fully saturating each section, and let process for 10 minutes - do not rinse.Apply No. 3 Hair Perfector (sold separately) over hair with No.0 applied to it, combing through as needed. Let process for a minimum of 10 minutes, then rinse, shampoo & condition.Brush or detangle hair before applying No. 0 so it can easily be absorbed. For thick, coarse, or long hair, work in small sections to ensure each area is fully saturated.OLAPLEX products are thoroughly tested in accordance with industry standards in-house and by independent third-party laboratories for safety and efficacy