Perricone MD Vitamin C Ester + Ferulic Brightening Serum 20% is a serum formulated with three forms of Vitamin C, equaling a 20% concentration. Also formulated with ferulic acid, the silky, lightweight serum helps to visibly brighten, smooth, and even the appearance of skin tone. After four weeks of daily use, the serum helps to improve the look of fine lines and wrinkles and uneven skin tone. After four weeks of daily use, 71% of participants showed improvement in the appearance of skin firmness/tightness based on cutometer testing. After four weeks of daily use, 80% of participants showed improvement in the look of skin texture based on visual grading. How do I use it: After cleansing, massage serum onto face and neck using a gentle upward motion. Wait until fully absorbed and follow with moisturizer (not included). Use morning and evening. Store in a cool, dark place. Product can oxidize and darken over time. From Perricone MD. Includes: