Martingale collars look similar to a traditional flat collar, but a short section of the collar is actually a smaller loop of either webbing or a chain with a leash attachment point. When clipped into a leash, it uses a limited amount of cinching to keep a dog from backing out of their collar.
You’ll sometimes hear them called no-slip collars, limited-slip collars, and even greyhound collars. “Greyhound collars” comes from the early inspiration for the design. Dogs whose heads are more narrow than their necks – like greyhounds and whippets – have a harder time slipping out of a martingale collar than they would a traditional flat collar.
They've grown in popularity among more than just slim-headed dog breeds. Any dog who has a knack for backing out of a regular collar can benefit from a martingale.