These leads are made from a soft, pliable diamond braid that comes with an adjustable leather slide to get a comfortable fit around your dog's neck. Each Martingale Lead has a diameter of 1/8" (3.18 mm) and length of 40" (1.02 m). Sizing chart Available in 3 different size collar loops: Small: 8" (20.32 cm) - Loop sizing adjusts from 12"- 18"Medium: 10" (25.40 cm) - Loop sizing 14"- 20"Large: 12" (30.48 cm) - Loop sizing 16"- 22"