RESISTANCE EXTENTIONISTE lenght strengthening shampoo 100 ml RESISTANCE EXTENTIONISTE lenght strengthening shampoo 100 ml is a strengthening shampoo from the Kérastase Resistance line. This shampoo is designed to strengthen and nourish weakened hair for a longer-lasting hair length. It is formulated with Pro-Keratin and Ceramides to help strengthen the hair fiber and protect it against breakage. It also helps to detangle hair and leave it feeling soft and smooth. This shampoo is best suited for medium to long hair lengths.