This Cosrx Snail Mucin Facial Serum drops from $25 to $13 at Amazon, saving you 48% off the regular price. This is the Black Friday price. It's been one of the top-selling beauty products at Amazon since last year. It uses natural snail secretions to smooth and hydrate damaged skin. It's hypoallergenic and safe for sensitive skin. Shipping is free with Prime or when you spend $35. Otherwise it adds $5.99.