Best Seller. Simple to use – the front athlete puts on a belt or shoulder harness, which is attached via strong Slastix resistance tubing to the belt or harness worn by the rear athlete. They then run in tandem, the front athlete receiving resistance training while the rear athlete receives overspeed training. This system allows both athletes to improve their training stride length and frequency. The Slastix resistance tubing provides a smooth, consistent pull for both athletes, while offering maximum safety. The swivel waist belt allows either athlete to change the direction of pull easily without forcing them to stop and remove the belt. Each harness system contains a carry bag, 20' Slastix tubing and two swivel waist belts.