For the dog that's the puller, the Gogo nylon martingale is the perfect answer.  Gives you the control with a gentle pull on the neck and keeps the little one a trained and happy puppy.   Adjustable and with a quick release buckle.  Comes in 3 sizes...xsmall 10"-12", small 14"-17" and medium 16"-21", and 5 colors...black, red, blue, pink and orange.