Higher Nature Colloidal Silver is easy-to-use and is made up of 10 parts per million (ppm) of the active ingredient, and purified water. It goes through a 9 step purification process to ensure a very small particle size of 0.0006 to 0.005 microns so that they have a proportionately large surface area for better effectiveness. Use the 200ml non-spray size to refill the 15ml and 100ml spray-nozzle sizes.