Formula C™, our Signature Exfoliating Antioxidant Serum is on sale. We now offer it in two different sizes, 1oz (30 ml) and 2 oz (60 ml). We also offer it in twin packs (two packs). The 1 oz twin packs are perfectly sized and convenient for travel. Whereas the 2oz are perfect for keeping one at work and the other one at home.