K18

K18 is the brand that brought patented peptide repair technology to hair, and its Leave-In Molecular Repair Hair Mask is the anchor — a bond-repair treatment that creators say has no direct competitor at the drugstore. The line also includes a lightweight hair oil that doesn't weigh hair down and a heat protectant that works internally. If you're looking for deep repair rather than surface-level conditioning, K18 is worth the investment.