"This product is for dogs with necks to 20"" and provides an added dimension of nighttime safety for you and your pet. The collar will reflect when light shines directly on the reflective strip. 2 in 1 reflecting flea & tick collar for dogs. Kills fleas and ticks common to dogs, including rocky mountain wood tick, carrier of rocky mountain spotted fever, and the deer tick, which may carry lyme disease. Use only on dogs."