(Innotek Pet) 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 correction. The correction is delivered through the contact points of the collar that touch his neck. He'll quickly associate the correction with the area you've declared off-limits. Quick and easy set-up: just place the rock and set the range, covers up to 16 feet in diameter. Adjustable collar fits pets 5 lbs. and larger, appropriate for neck sizes 6" – 28”.