GENDER: Unisex / Damaged hair? Strengthen it with this leave-in hair serum that completes the Bond Repair routine. For the first time, our Bond Repair formula is supported by Citric Acid. Inspired by salon hair care: At a molecular level, there are millions of hair bridges in the hair that determine the structure and strength of the hair. When these break through brushing, bleaching, heat and colouring, the hair becomes weak and damaged. Our formula with citric acid goes beneath the surface of the hair into the interior of the hair, the cortex, to rebuild broken hair bridges.