Easily attached to your pet's existing collar, this water resistant digital ultrasonic collar operates all High Tech Pet Power Pet electronic pet doors. Using all digital circuitry, High Tech Pet's proprietary state of the art design provides a stronger signal and maintains better accuracy over all temperature ranges. It includes a specially designed B3V1A premium quality battery which lasts about 3 - 4 months and prevents damage to the circuitry if the battery is accidentally installed incorrectly. With a fully enclosed ultrasonic speaker, the MS-5 is waterproof and rugged. It's perfect for the pet who likes to do some serious "ruff housing". The MS-5 is fully immersible for short periods and will continue to work when wet. It will stand up to heavy rain showers and is perfect for dogs who love to play in the snow. Beware of knock-off products which do not produce the full digital code needed to open your Power Pet door every time. Small and lightweight, one size fits all dogs and cats. A small screw secures the battery compartment door for extra safety. Comes with a protective boot that allows you to attach the MS-5 to your pet's existing collar. This is a quality product from the company who invented it.