Vitamin C may not be the new kid on the skin-care ingredient block, but it remains one of the most popular year after year. Building on the success of their Violet-C Radiance Mask, this new oil- and fragrance-free serum packs a whopping 20 percent concentration of vitamin C (and two different types at that) to deliver both instant and long-term results. A 10 percent concentration of AHAs joins the mix, too, all working together to leave your skin firmer, smoother, and noticeably more glow-y.