iHerb guarantees that you will receive the best overall value in the world for over 30,000 natural products -- all authentic brands sold in the U.S. market, so long as you order at least once every 60 days. We will also guarantee the delivery of your order.iHerb`s distribution centers are entirely climate-controlled, which protects the products from such conditions as humidity, heat and cold. In addition, our distribution centers are industry-certified by NSF International, earning Good Manufacturing Practice (GMP) certification.