The coil design allows for the leash to take up its own slack as the dog moves closer to your heel which prevents dragging. Great for jogging or hands free walks. Leash will help prevent tangling if you are walking more than one dog. Coil will not wear out and lose its "spring" like similar products made with Bungee. Coiled leash can also double as a hand leash by clipping one of the ends to the body of the coil to form a handle. Coil can also be used as a car restraint in most vehicles by wrapping the coil around any bucket seat and clipping the lose end to pet harness.