Key Benefits Intensifies repair results with N°3 Strengthens hair and reduces breakage Rebuilds hair bonds at a molecular level Prime your hair for your deepest at-home repair with this salon-inspired pre-treatment to boost the effects of N°3 Hair Perfector™. The highly concentrated formula rebuilds disulfide bonds to repair more severe damage and immediately strengthens hair when N°0 is used with N°3. How To Use On dry hair, apply and distribute evenly from root to tip. Leave on for 10 minutes. Do not rinse. Apply N°3 Hair Perfector™ and comb through. Leave on for 10 minutes. Rinse well. Shampoo and condition with N°4 and N°5. Use as a two-part system with N°3 once a week or 2-3x per week for very damaged hair.