Prep + Prime Moisture Infusion Serum is a lightweight formula that saturates the skin with a concentrated boost of hydration, making it a unique hybrid between skincare and primer. It gently soothes, revives and replenishes the skin while preparing it for foundation. How to use: After cleansing, apply a desired amount to your fingertips and blend over the face. Follow with your daily moisturizer if desired. 1.7 oz. By M?A?C.