* Proven Safe and Effective When Used as Directed * Effective up to 4 Months * No Harsh Ingredients * Repels Fleas, Ticks & Mosquitoes * Diffusing Collar for Small Dogs & Puppies * Fits Necks up to 27" * Laboratory Tested - Veterinarian Approved Using active herbal ingredients, Dr. Mercola Herbal Repellent Collar for Large Dogs effectively controls fleas, ticks, and mosquitoes, reducing the number of bites.