Power-Brightening Pure Vitamin C Serum: COSRX’s Advanced The Vitamin C 23 Serum features a high strength 23% pure vitamin C with Super Vitamin E and Glutathione to target uneven skin tone, early signs of aging, and dullness. Ideal for experienced vitamin C users seeking visible brightening and firmer skin, it absorbs smoothly to leave the complexion more radiant, supple, and revitalized. Size: 20ml / 0.67fl. oz