**What It Is**: A jumbo-sized version of Sunday Riley's brightening serum. **What It Does**: With a 15% infusion of THD ascorbate - a potent, ultra-stable form of vitamin C - this fast-absorbing formula fights the appearance of dullness and discoloration while helping boost radiance and brightness for a glowing complexion. **How to use**: Apply one to two pumps of serum to cleansed skin; we recommend using both day and night. **Key Ingredients** * Vitamin C: A sought-after ingredient in most modern skincare, vitamin C stimulates the production of collagen and helps to reduce the appearance of fine lines and wrinkles over time. When used on a regular basis, it helps to fade acne scars and reduce discoloration, improving the texture and tone of the skin.