Monthly flea and tick preventative is a must for all types of sporting dogs and the Original K-9 Advantix Flea and Tick Treatment is thorough and economical. A fully waterproof monthly topical treatment, K-9 Advantix repels fleas, ticks, mosquitoes, biting flies and chewing lice, as well as kills adult fleas and ticks that may already be on the dog. Each package contains 4 vials of treatment, enough to treat one dog for 4 months, or 4 dogs for one month. To apply, you simply snap the end off of the vial, then rub the liquid into the fur and skin of the dog along the spine, from the neck to the base of the tail. Please weigh your dog prior to ordering to ensure proper dosage: Small is for dogs less than 10 lbs., Medium is 11-20 lbs., Large 21-55 lbs. and X-Large is for dogs 55 lbs. and over; please specify when ordering.