Bayer K9 Advantix II Flea Treatment is a once-a-month, topical application for large dogs and puppies at least 7 weeks of age and weighing between 21-55lb. It both kills and repels fleas, ticks, mosquitoes, biting flies and lice. K9 Advantix II contains imidacloprid, permethrin and pyriproxyfen that work together to repel and kill parasites that can potentially transmit disease-causing organisms to your dog. This waterproof formula is designed to kill all life stages of fleas and prevents the development of flea eggs, larvae and pupae within 12 hours. Package contains 4 monthly applications.