The Seresto Flea and Tick Collar for small dogs is a revolutionary, convenient collar designed to offer extended pest protection for up to 8 months. Ideal for dogs under 18 lbs and as young as 7 weeks, Seresto’s sustained release technology continually supplies two active ingredients, imidacloprid and flumethrin, to your dog's skin and coat. This collar repels and kills fleas and ticks on contact—no biting required—reducing the risk of disease transmission.