Your Stamina AeroPilates reformer is easily upgraded to add resistance to your strength training goals. Each cord two included adds 40% more resistance than the original cords that came with your Stamina AeroPilates reformer. Replacing the cord on your reformer is easy and instructions are included.. For use with any Stamina AeroPilates reformer Increases tension by 40% over original cords Easy installation Recommended Use Replace one or two black resistance cords with one or two red power cords to increase tension by 40% Construction Elastic cord, nylon cover, plastic knob Color red, black Resistance 40% more resistance than one regular black cord Comfort Elements Target Training Includes Two power cords, installation instructions Assembly Installation required Warranty 90 days