The Spectra Shield Collar Attached Medallion offers 4 months of flea and tick control for dogs. It is approved for use on dogs 6 months and older (DO NOT USE ON CATS). The medallion is a convenient alternative to monthly treatments. It is quick and easy to use, just clip"n go! No more hassle remembering to apply every month and it can be worn during swimming or bathing. Spectra Shield - Sustained Release Delivery System: continuously releases very small amounts of active ingredients, consistently replenishes the actives to the dog"s skin and hair coat and avoids heavy concentrations and variations of active ingredients.