100% Nylon Heavy Duty Cord for replacing leash- cord on walky dog and walky dog plus. Replacing the cord is extremely easy instructions included and link to watch video. Cord comes pre knotted and sized from factory for easy replacement. 100% Nylon Heavy Duty paracord. Made In USA. Manufactured by a certified US government contractor. Diameter: 5/32". Over time, powerful dogs may tend to wear down the standard cord that comes with the WalkyDog. This does not happen over night, but it is nice to have extra cord when needed. Replacing the cord is extremely easy instructions included and link to watch video