The collar does not stretch itself. Martingale collar is a slip collar **WITHOUT THE BUCKLE**, which is designed for sighthouds but becomes popular with other breeds. 

The martingale collars provide more control over the dogs without the choking effect of a slip collar. Great for preventing escape. Properly fitted, the collar will be comfortably loose whenever the dog is not pulling against the leash
Polyester fabric with high density webbing to add durability; This collar is a single product.