The basics A professional-inspired treatment that primes hair for deeper repair with the highest dose of patented OLAPLEX technology in any take-home product. The benefits It rebuilds hair bonds, strengthens and protects hair integrity. The uses Use as the first step in a two-part system with N°.3 Hair Perfector. The bottom line 68% more repair & 3x stronger hair when used as a two-part system in just one use. N° 0 bottle should last 3-6 applications, based on hair length and density.