Maxtronic Portable Wireless 2 Dog Fence, NO Wires to BURY-800FT Containment System Create a safe outdoor area for your pets without a physical fence. Adjust your pet's boundary from 3 to 800 feet in all directions from the indoor transmitter. Updated Collar, More Save Power, Receiver Collar is Rechargeable and Water Resistant with Low Battery Indicator. Please charge the collar full before using for the first time. Updated Transmitter with Build-in Battery, Keep Working without 110V AC Power for 24 Hours. An unlimited number of pets can be added to the system.