The medallion snaps on easily to the dog’s collar so there is no mess and no stress! It is available in 3 different weight sizes. The medallion contains a powerful synergized pyrethroid - zetacypermethrin - that kills adult fleas and ticks at maximum efficacy. The second ingredient, Piperonyl Butoxide, is a mixedfunction oxidase inhibitor which ensures the maximum effectiveness of Spectra Shield against ticks during all stages of their blood-feeding life cycle. While this highly effective combination protects pets, it exhibits very low toxicity to animals and humans.