This is a medical grade 15% Vitamin C Serum. 
This formulation is magnesium based.
This means it is less likely to irritate acne and rosacea prone skin, unlike the L-Ascorbic vitamin C. 
This serum also contains hyaluronic acid and Vitamin B5 to hydrate and smooth.

Size:
Retail 0.5 fl oz (15ml)
Professional 1 fl oz (28ml)
 
Ingredients:
Water, Magnesium Ascorbyl Phosphate, Sodium Hyaluronate, Pentylene Glycol, Panthenol, Phenoxyethanol, Capryl Glycol, Hexylene Glycol