i am a dog trainer so i just thought i would mention it.
Also the the person that says it looks painful, this is not as bad as it looks. the prongs close together causing a slight pinching of the skin around the dogs neck. the dog will in most cases feel the pressure start to apply and stop pulling. This type of correction is applied by the dog itself. If he/she pulls, they get a slight pinch, if they do not, no pinch. the human should not be pulling on the collar at all. Also I have used these collars on my own arm and felt the pressure that would be used and although uncomfortable it is not horrible. As a dog trainer i find that there are some cases when this collar is needed. Not all dogs need it, each one is different. Also if you are using this you should get the help of a dog trainer or vet for showing you how to fit it. the links can be removed and added to make the collar smaller and/or bigger. a proper fit is a must with this collar.
fits small to medium sized dogs. I used it for my mini australian shepard so if you know what that is its a good size indicator. I will measure it and let you know later.