This is the big one. Environ's C-Quence Serum 4 Plus is the final and most potent level in their Youth EssentiA range – ideal for skin that’s already worked its way up through the step-up system. It’s packed with the highest levels of vitamins A, C, and E, plus powerful peptides, antioxidants, and hyaluronic acid to target everything from fine lines and dullness to texture and tone.