CosMedix Pure C Mixing Crystals are 100% pure L-Ascorbic Acid in a non-irritating and stable, crystal form. CosMedix Pure C provides Vitamin C to the skin in its most bio-available and absorbable state, which can be mixed easily with any CosMedix product. This potent antioxidant is kept in powder form to ensure a fresh dose with maximum potency each time you use it.