I bought this product because of a huge deal they had going on, and I have never been happier with a hair product. Their shampoo is one of the only shampoos that easily lathers, cleans my hair and scalp well, and leaves my hair squeaky clean. I have tried just about every product and just the basic 3, 4, & 5 are amazing to start with. I frequently use No. 3 as a hair mask, No. 4 about once a week to two weeks, and No. 5 if my hair is feeling extra dry. I am a huge fan of this company and have just purchased in bulk! Thank God for Olaplex- my hair loves you.