Advantage II for cats is for use on cats and kittens 8 weeks of age and older and weighing over 9lbs. Advantage II kills fleas through contact, effectively breaking the flea life cycle - so you can help protect your cat from the fleas you see and the ones you don't. Advantage II uses two active ingredients for flea prevention and treatment. Imidacloprid kills adult fleas on the animal. The insect growth regulator pyriproxyfen inhibits development of immature stages, effectively breaking the flea life cycle. For fleas only.