Each small batch of colloidal silver is manufactured with high voltage AC 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 and a 32 ounce refill are both available with a screw top lid.