Intensive Bond Building Hair Treatment N°0 is an intensive repair booster developed by Olaplex to be used as a pre-treatment before applying Hair Perfector N°3. Through the two-step treatment, N°0 and N°3 are able to repair broken disulfide bridges in the hair and provide a lasting improvement to the overall hair structure. Scientific studies have shown that when the two treatments are used together, there is a 68% increase in repair and 3 times stronger hair. Depending on hair length and density, a bottle of N°0 can be used up to 3-6 times.