The Barrier Transmitter, disguised as a rock in your landscape, sends a circular radio signal to your pet's receiver collar. When your pet enters the barrier area, he'll hear audible tones from the receiver collar followed by a safe, progressive static stimulation. The stimulation is delivered through the contact points of the collar that touch his neck. He'll quickly associate the stimulation with the area you've declared off-limits. Protects an area up to 4.8 m (16 ft) in diameter. Receiver Collar fits pets 3.6 kg (5 lb) and larger, appropriate for neck sizes 15 cm - 70 cm (6" - 28").