Martingale Collar The Martingale collar is a dog collar composed of two parts, one fixed and one sliding. The fixed part contains two rings, where the movable part is placed to attach the leash to the collar. The Martingale collar is the favorite collar for greyhounds. Ideal for dog breeds with heads as narrow as their necks, such as greyhounds and podencos, although this type of collar has become a valid solution for all types of breeds, especially large breeds. A true escape-proof collar. It is almost impossible to escape from a properly adjusted Martingale collar. By adapting to your dog's neck, if it tries to escape, it won't be able to pull its head out.