Bayer K9 Advantix II 4 Pack Topical Prevention & Treatment of Ticks, Fleas, Mosquitoes, Biting Flies & Lice for Small Dogs. This veterinarian-recommended monthly flea, tick, and mosquito treatment kills through contact, eliminating and preventing flea eggs. Waterproof after 24 hours, it provides continuous protection for up to 30 days, even after bathing or swimming. Suitable for small dogs and puppies 7 weeks and older, weighing 4-10 lb. Contains four 1-month applications.