Dr. Mercola Herbal Repellent Collar for Large Dogs with Natural Active Ingredients, Long-Lasting Flea Prevention - Odorless, Safe and Waterproof Flea Collars Effective Up to 4 Months, Necks up to 27" EFFECTIVE UP TO 4 MONTHS: The formula used in our collars will keep the protection effective up to 4 months; therefore, you can save more time and money than using other medications. Your dog no longer has to suffer from itchiness and discomfort. WATERPROOF COLLAR: An advantage of our dog collars is the water-resistant design, which allows it to normally perform the function even in the water. HERBAL REPELLENT COLLAR: Dr. Mercola herbal repellent collar is free of harsh chemicals, using a special blend of oils that allow it to work for up to 4 months. Unlike other pest repellent collars, the active ingredients are included as a physical part of the collar, allowing them to be diffused over a long period of time  making it much more effective. FOR DOGS, PUPPIES AND CATS: The Herbal Repellent Collar is one of the safest, most convenient insect repellent options for your pet. Helps repel ticks, fleas, lice, pests out of your pet. 100% MONEY-BACK GUARANTEE: Dont worry about money, we are so convinced in our herbal repellent collar that if they don't live up to your expectations you can send them back for a full, complete refund so you have nothing to lose! Veterinarian recommended for large and small dogs, puppies over 4 months old, cats, and kittens Completely toxin-free, using a special blend of highly-effective oils Superior in advanced flea, tick, and mosquito essential oil protection for up to 4 months An advanced option for long-lasting pest protection