The MB-1 is a battery-operated mobile boundary that can be used either indoors or outdoors. It is weatherproof for outdoor use and it has a rechargeable battery. It is wireless (used without a boundary wire), so it is easy to set up wherever you need it. Creates a pet-free zone up to 8 feet in diameter (4 feet from the center). Includes MB-1 transmitter, battery charger, and four indoor training flags. Works with all DogWatch FM receivers. Receiver collars must be purchased separately.