Youth EssentiA #4 kit contains the highest concentration of vitamins A and C and is the fouth level in the Youth EssentiA range step-up system. Additional vitamin C is added to the serum by including Environ c-boost to your regimen, improving the overall radiance of the skin, and appearance of a more refined tone. Also included is the c quence eye gel, a technologically advanced gel that contains essential vitamins A & C, antioxidants and specially selected peptides to assist in hydrating the skin, improving the appearance of fine lines and providing daily defense against the harsh environmental influences that promote aging. It is recommended to use the highest step comfortable, for the best in skin care. Also included is the c quence eye gel, a technologically advanced gel that contains essential vitamins A & C, antioxidants and specially selected peptides to assist in hydrating the skin, improving the appearance of fine lines and providing daily defense against the harsh environmental influences that promote aging. It is recommended to use the highest step comfortable, for the best in skin care.