Double Wood's Colloidal silver combines only distilled water with 99.9% pure Colloidal Silver. It is also stored in a glass bottle to ensure the product stays safe and fresh. Our 20mcg recommended dose can be easily measured with droppers included in the bottle itself. Additionally, our dose is far below the safe daily dose established by the EPA of 350mcg per day. Double Wood's 99.9% pure Colloidal Silver 20 PPM liquid drops are Made in the USA, Non-Gmo, and Gluten Free. Each bottle contains 120 servings of 20 PPM colloidal silver (total of 4 fluid ounces). This is enough colloidal silver to last a whopping 4 months!