Increase the size of your existing wireless fence boundary with the Stay & Play® Wireless Fence Extra Transmitter. Simply place the transmitters with an overlapping boundary of 30 feet and it will increase your pet's play area. Trust PetSafe® to help keep your pet healthy, safe and happy. Features Extra transmitter to expand your pet’s play area Circular boundary adjusts to cover a 3/4-acre yard (22-105 ft in all directions) Our proprietary circular boundary gently guides your dog back to his play area, giving you the most accurate wireless fence experience Doesn’t include a receiver collar, sold separately