Advantage II Cats: 12 Month Supply New Formula with IGR. Kills all life stages of fleas and contains Imidacloprid which acts to disable a flea's nervous system. Once a month topical flea prevention and treatment for cats, for use only on cats 8 weeks and older. Features: Kills all flea life stages, preventing fleas on treated pets from infesting your home. Kills adult fleas already on a pet within 12 hours and re-infesting fleas within 2 hours. Waterproof Fast and easy dermal application Only one application a month necessary Safe on Cats 8 weeks and Older Item Specifications: Weight: 5-9lbs - Orange Over 9lbs - Purple Application: Apply entire contents of tube on the neck at the base of the skull. Monthly application. Length of Effectiveness: Under normal conditions, the product is effective for a month. However, in cases of severe flea infestation, retreatment may be necessary earlier than four weeks. Do not retreat more often than once every seven (7) days. After flea control is attained, return to a monthly retreatment schedule. Active ingredients: 9.1% Imidacloprid 0.46% Pyripoxyfen 90.44% other ingredients