The MuscleDriver USA Overspeed Trainer is a two person training tool and perfect for rapid speed development. The Overspeed Trainer comes with a nylon covered industrial grade rubber tubing with latches on each end, two harnesses, and a carrying bag. The tube allows for an elastic pull to help aid the back runner to stay at pace with the front-runner. The elastic has a 3ft stretch capacity and is restricted by the nylon covering from overstretching the rubber tubing and prevents dangerous situations of the tubing breaking and snapping back to either runner. This product has a 2-year guarantee only if the nylon covering remains over the tubing. If covering is removed this voids all guarantees.