Ester C?? Complex capsules contain a non-acidic, calcium ascorbate form of vitamin C combined with a potent citrus bioflavonoid complex. Ester-C?? is a unique form of vitamin C that is created through a patented, water-based process that combines vitamin C and calcium. Ester-C?? is non-acidic and should be well-tolerated by those who are sensitive to the acidic nature of ascorbic acid.