COSRX Pure Vitamin C 23 Serum 20mlCOSRX Pure Vitamin C 23 Serum 20ml Vitamin C is one of the most researched and widely validated brightening actives in skincare but not all Vitamin C serums are equal. The active form that actually works is L ascorbic acid (pure Vitamin C), and its effectiveness depends heavily on concentration. COSRX Pure Vitamin C 23 Serum 20ml delivers a high potency 23% L ascorbic acid in a K beauty formulation designed to address hyperpigmentation, dullness, fine