A quality dog collar can make a huge difference when training your pup. Martingale collars are a great option when looking for the best collar for medium dogs. They allow you to have gentle control when walking/training medium dog breeds like Border Collies, Greyhounds (who are often known to slip out of regular, flat collars due to their thin necks), and Brittanys. We like the Country Brook Petz Martingale Heavy Duty Collar. It comes in 20 plus colors and boasts that it’s escape-proof so you won’t have to worry about your medium dog weaseling their way out of it. It’s also a very affordable option, coming in under $10. As with any martingale collar, you should only place one on your dog when supervised.