Nutricost's Colloidal Silver contains 30 ppm per dose of pure, high quality colloidal Silver. Nutricost packaged this in Cobalt Blue glass bottles to protect the stability and quality of the Colloidal Silver. The blue glass helps protect the stability by filtering UV light and glass, unlike plastic bottles, does not leach impurities into the silver. Each bottle contains 4oz and this size also includes a convenient serving dropper.