The PetSafe® Wireless Pet Containment System™ includes a portable, wireless transmitter that covers an adjustable circular area of up to 1/2 acre (180' in diameter) and a receiver collar with 5 intensity levels. The tone-only mode beeps to alert your dog when he or she approaches a boundary area. Recommended for dogs weighing at least 8 lb. with a 6" - 28" neck.