Collars are adjustable for growing dogs.   About Martingale CollarsMartingale collars are designed to prevent a dog from escaping from their collar while on a leash. Martingales are constructed with 2 loops. The larger loop goes around the dog’s neck. The leash is then attached to the D ring on the smaller loop. When the dog attempts to pull their head out of the collar, the tension from the leash, attached to the D ring on the smaller loop, makes the larger loop tighten around the dog’s neck, behind the ears to prevent them from escaping or “backing out” of the collar.Martingale collars are sometimes referred to as Training or Correction collars. On some martingale collars, the smaller second loop is actually a chain.Martingale collars should only be worn when the dog is on a leash. Martingales should be removed when the leash is taken. We strongly recommend that a professional dog trainer be consulted before using any type of choke collar. Positive training methods should be attempted first. To find a certified trainer in your area contact the Association of Pet Dog Trainers www.apdt.com/