Peppermint Flea & Tick Collar repels bugs and is an added layer of protection against fleas and ticks for up to 4 months, mosquitoes up to 1 month. Use with Flea & Tick Pets Home spray to protect your pet. One size for dogs (up to 21" neck) 4 months or older. Active issue? Collar doesn't kill bugs. Use Flea & Tick sprays for pets, home and yard as directed.