The metal tag contains silicon dioxide particles that are encoded with frequencies that the tag then emits over time. These frequencies are annoying to pests, so they stay away from the pet wearing the tag. The tag is also encoded with frequencies that will synchronize with your pet's own unique biological frequency, which helps to support their immune system. This is why the tag must be kept on or near the pet at all times, and why it takes a few weeks for it to reach maximum effectiveness. A strong immune system is part of a strong defense against pests, because pests are more attracted to animals with a weaker immune system.