The C5 Super Boost Moisturizer is made with two highly stable types of vitamin C: 3-O ethyl ascorbic acid (3%) and ascorbyl glucoside (2%). The 3-O form is both water- and oil-soluble, while ascorbyl glucoside is water-soluble. Together, they deliver multi-level vitamin C benefits. Skin converts 3-O ethyl ascorbic acid and ascorbyl glucoside to L-ascorbic acid, the most research-backed form of vitamin C. L-ascorbic acid helps fight off free radicals and external stressors, lessening the ageing impact of both.