Medik8 c tetra is a revolutionary ultra stable vitamin c serum which helps combat sun induced damage to the skin trigger collagen synthesis increase the skin s elasticity and density as well as improve the skin s 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 fr