Hartz Flea and Tick Collar kills ticks and fleas for 7 months. Adjustable Fits Necks Up to 15 Inches. These collars are available in various colors and are waterproof. Swimming rain and getting them wet do not reduce efficiency. For use on puppies 6 weeks of age or older. Each Package Comes with 2 Units Flea Collar for Puppies. Pictures may be magnified to show detail. For further information on size, color, conditions please refer to the item description or please ask a question before buying.