PER4M Jump Trainer for Jumping, Plyometrics and Resistance Training that Doesn&rsquo;t Stress Joints &ndash; Perfect for Basketball, Volleyball and Track & Field Improve vertical leap and lower body strength Works with jumping, plyometrics and resistance training Weight free jump resistance doesn't stress joints Padded adjustable belt and ankle straps fit most sizes comfortably Quick release power tubes are easily added and removed