The Medik8 C Tetra Serum Pro-Collagen Vitamin C Serum is a revolutionary ultra-stable vitamin C serum which helps combat sun-induced damage to the skin, trigger collagen synthesis, increase the skins elasticity and density as well as improve the skins texture and brighten the complexion. Designed for both men and women in their mid-20s to 40s. Regular vitamin C is very unstable and many typical vitamin C products are inactive by the time they are used on the skin, in some cases, they have become pro-oxidant and actually generate free radicals! Ground-breaking stability data on C-Tetra guarantees real vitamin C activity and best of all, unlike L-ascorbic acid (regular vitamin C), C-Tetra will not exfoliate or irritate skin. C-Tetra® contains 3% Tetrahexyldecyl Ascorbate, the most potent and highly stable derivative of vitamin C available. C-Tetra has been shown to have upto 4 times the potency L-ascorbic acid and other derivatives such as MAP (magnesium ascorbyl phosphate).