COSRX - The Vitamin C 13 Serum 20ml Description Information - COSRX The Vitamin C 13 Serum is the milder version of the previous The Vitamin C 23 Serum, suitable to use everyday like a daily vitamin for your skin! A dark spot care serum with 13% highly concentrated pure Vitamin C, this serum works to improve hyperpigmentation and even out the skin tone. Featuring a hypoallergenic and stabilized formula, this serum is perfect for those looking to prevents the early signs of aging & recovers their overall skin health. With the help of Allantoin & Tocotrienol (Super Vitamin E), it also helps to increase collagen synthesis and improve the skin's overall elasticity.