Small is appropriate for dogs weighing 4-10lb
Medium is appropriate for dogs weighing 11-20lbs
Large is appropriate for dogs weighing 21-55lbs
X-Large is appropriate for dogs weighing over 55lbs
K9 Advantix II is a convenient monthy topical application that kills and repels fleas. ticks and mosquitoes, kills lice and repels biting flies. It's specifically formulated for dogs with imidaclopid, permethrin and pyriproxyfen for broad-spectrum protection against these ectoparasites that can transmit diseases to your patients. And because it kills through contact, there's no biting required.