The Pet-Temp Instant Ear Thermometer is a fast, easy, humane, accurate, safe and clean pet thermometer. The only ear thermometer designed specifically for animals. The unique, ergonomic, animal-friendly design measures heat from the deep horizontal ear canal giving an accurate "core" body temperature. A great alternative to messy rectal thermometers. Accurate on dogs, cats, puppies, kittens, rabbits, guinea pigs, ferrets and chinchillas. Built-in lithium battery lasts up to 5 years. Comes with 20 disposable lens covers.