COSRX The Vitamin C23 Serum is the ultimate Vitamin C Serum formulated with 23% pure Vitamin C, to reap all the benefits this ingredient has to offer. Vitamin C helps to brighten your complexion, as well as even out your skin tone, reducing hyperpigmentation and also has anti-aging properties. The Vitamin C works together with the added Vitamin E, to make your skin glow and clear away blemishes.