If you are looking for a way to treat damaged or weakened hair, then try one of the best hair care products available. Smooth and strengthen weak or damaged hair with Kerastase Resistance Fondant Extentioniste. This product works effectively on many different hair types, and each use takes only 2-3 minutes. The Creatine R Complex reinforces the internal structure of the hair, while maleic acid seals the cuticle from root to tip.