OLAPLEX® No.4P BLONDE ENHANCER™ TONING SHAMPOO strengthens, softens, and neutralizes unwanted yellow tones for brighter, more manageable hair. The sulfate-free, highly concentrated formula allows for customizable toning -- The longer you treat, the brighter the results. HOW TO USE: Apply to wet hair. Lather fully & let process 1-3 minutes. Rinse. For more intense toning, leave on up to 5 minutes. TIP: If hair has product buildup, cleanse first with No.4 BOND MAINTENANCE SHAMPOO.