Hartz Ultra Guard Flea & Tick Drops 60lbs. Hartz UltraGuard Flea and Tick Drops offer affordable protection against adult fleas and ticks. With convenient once-a-month application, this reliable product kills fleas and ticks and repels mosquitoes. Includes formulas created especially for dogs or cats; these products are not interchangeable. Available is dosages appropriate for different sized pets.