If you're not familiar with martingale collars like this one they are designed to provide just enough cinch in the neck give your dog a message when he pulls, but not enough to cause discomfort. I like them because you get to set the amount of cinch yourself when you adjust the collar size. The Ruffwear Web Reaction Collar is well suited to communicate with your dog about the pace of the walk. Never end up holding a leash with an empty collar! If your dog can outsmart the average collar I'm talking to you! The beauty of a Margingale collar is it cinches tighter when your dog stops, backs up or tries to slip out of the collar. This style is really perfect for dogs with smaller heads like greyhounds and whippets. See also the Chain Reaction Collar for a Ruffwear martingale style collar.