Redesigned for a quick and targeted stream application, the No.0 Intensive Bond Building Hair Treatment features an easy to use nozzle that primes the hair and delivers the highest concentration of the patented bond building technology of any OLAPLEX at home product. Use as the first step in a two-part at-home system with No.3 Hair Perfector (sold separately) to strengthen and repair all types of damaged hair. Scientifically Proven: 68% more repair & 3x stronger hair* *When used as a two-part system in just one use. APPLICATION TIP: N°.0 bottle should last 3-6 applications, based on hair length and density."