Made from the industry’s gold standard of vitamin C, L-ascorbic Acid, our vitamin C serums are formulated at pH levels shown to optimize stability, permeability, and efficacy -- instantly absorbing into the skin for lasting results.* L-Ascorbic Acid is effective in reducing the appearance of fine lines, wrinkles and photoaging of the skin. 91% of users reported skin appeared bright and/or more hydrated** Professional-C Serum 20% provides 5X better absorption levels over another leading competitor. Consumers prefer Obagi Professional-C Serum 20% nearly 2 to 1 over another leading competitor. *When used consistently over time. 1 Percutaneous Absorption Study. Data on file at Obagi Cosmeceuticals LLC.