Advantage II Flea Prevention For Cats 8 Weeks, Over 9 lbs Purple 2 pack Kills adult fleas fast before they lay eggs. Stops biting in 3-5 minutes. Kills flea larvae before they develop into biting fleas. Kills Flea Eggs before they hatch Gentle enough puppies and kittens as young as 7 weeks and small dogs under 11 lbs.