Flea & tick collar for dogs & puppies 12 weeks & older. One size fits all. Comfi fit. Secure dual buckle system. 2 six month collars for 12 months of continuous protection. Kill: Fleas & ticks. Repels: Mosquitoes (Except California). Prevents: Flea eggs from hatching. Full body protection. Each Hartz UltraGuard ProMax flea & tick collar for dogs & puppies 12 weeks & older collar provides 6 months protection against fleas, ticks and mosquitoes (Except California) worn at a time, providing a total of 12 months protection against fleas, ticks and mosquitoes (Except California).