Each small batch of colloidal silver is manufactured and tested for highest quality and potency. It is calibrated at 20 ppm (parts per million). Silver is naturally anti-bacterial, anti-microbial, and anti-fungal. It is gentle enough to be used in the eyes and ears, so perfect for helping prevent infections at the first sign of them. You can choose a 2 ounce bottle with either a spray or dropper top. An 8 ounce refill with a screw top lid is also available.