The martingale-style collar tightens to allow control and reduces the risk of a dog backing out of his collar. Martingale collars have 2 loops (as shown). The smaller loop attaches to the lead and is for control, it tightens when pulled. The second loop adjusts to properly fit your dog. • Prevents dog from slipping out of the collar • Tightens when dog pulls and loosens when dog stops • Perfect for dogs who are prone to escape and breeds with necks larger than their heads • Not recommended for tie-out use