The Homerun Slugger is for strength training for batters. Designed to strengthen only the muscles that it takes to swing a bat. This machine is used just like strength training for a body builder. You increase your strength by add resistance bands. With this machine you will not plateau, adding resistance bands as you go. It is designed to help the batter hit the ball farther. The faster you swing the farther the ball goes. The system of homerunslugger is patent. No other patent exist on this system.