The Hartz UltraGuard Plus Flea & Tick Dog Collar is formulated to effectively kill both fleas and ticks for up to 7 months. This treatment also prevents flea eggs from hatching, thereby preventing reinfestation. The Hartz UltraGuar Plus collar provides a fresh scent and is water resistent. This product is for use on dogs an puppies 6 weeks of age and older.For dogs with necks up to 23 inches. Water resistant. When your dog has fleas and ticks, your family and pet may be exposed to: Lyme disease, tapeworm infestation, flea bite anemia, flea allergy dermatitis.