Up Country Martingale collars are a gentle way to have control over your dog. Perfect for dogs that pull or easily slip out of their collars, Martingales create an even tension around the neck avoiding neck and throat injuries. These collars are made from high-tensile strength nylon webbing with sewn on polyester/nylon ribbons. They are stain and fray resistant; designed to last a lifetime. All collar and lead hardware is cast, not welded brass. For measuring, use a soft tape measure (tailor's tape measure) or a piece of string or ribbon to measure your dog's neck size. Purchase Small for necks measuring between 9 inches and 15 inches, Medium for necks between 12 inches and 18 inches Large between 15 and 21 inches and X-Large between 18 and 24 inches.