Kérastases salon-favourite range is so extensive, youd be forgiven for having trouble pinpointing just the right formula, but the Bain Extentioniste is specifically formulated to help strengthen hair and increase elasticity, making it perfect for those looking to keep long hair healthy and shiny. Amino acids and lipids help strengthen fibres from the inside out, while taurine helps to purify and stimulate the scalp to keep your long hair journey on the right track.