PetLock Max is a monthly topical treatment and preventative of ticks, fleas, mosquitoes, biting flies, & lice. PetLock Max long-lasting, waterproof formula has three active ingredients: Imidacloprid, Permethrin, and the IGR (insect growth inhibitor) Pyriproxyfen that prevents the flea eggs and larvae from developing into biting adults. These are the same active ingredients used in other popular spot on treatments offering you and your pet trusted flea protection at a fraction of the cost. Dogs 5-10 lbs – 4 Pack