Obagi Professional-C® Serum 15% 30ml helps to fortify skin and safeguard a more youthful appearance. Formulated with pure L-ascorbic acid to optimize efficacy, and permeability. Obagi Professional-C Serum 15% is a highly concentrated serum with antioxidant L-Ascorbic Acid for most skin types. L-ascorbic Acid is known to support new collagen production and is also effective in reducing the appearance of fine lines, wrinkles and photoaging of the skin.