Bayer Advantage 40 (Green) Spot On for Small Dogs, Cats or Rabbits (3-10 Lbs) 4 Month Supply Use on small dogs, rabbits and cats weighing up to nine pounds (4kg) and kittens aged above eight weeks. Kills all fleas in 24 hours. Starts killing fleas in 20 minutes. 4 pipettes for four 4 months of protection. Can be used on kittens over the age of 8 weeks.