The Canny Collar is the best collar to stop your dog from pulling on the lead. A snug measurement is important to ensure the collar cannot come off over your dog's head. To choose the correct size Canny Collar for your dog, measure your dog's neck to just behind the ears as shown by the red arrows. The Canny Collar will sit generally higher than your dog's regular collar at a point where the neck is narrower, though if it naturally falls down the neck, it will not affect the functionality.