Exercise u0026amp; strengthen muscles in the upper u0026amp; lower body to build strength, increase motion and improve conditioningnImproves strength, range of motion and flexibility in a simple to use, portable product that works in the clinic, the gym, at home or on the roadnColor-coded Progressive Resistance system allows users to recognize improvement as it happens, as you grow stronger you can move up to the next colornRehabilitate muscles through simple yet effective workouts to increase strength u0026amp; improve motionnSpecial Heavy Black Tubes are the sixth of eight levels of resistance and great for rehabilitation and higher level resistance, they offer 7.3 lbs. resistance and 25% increase from preceding color at 100% elongation and 10.2 lbs. at 200%n10-1316 Size / Color: XX-Heavy / Silver Item sold separately Features: -Made of natural rubber.-Resistance levels, obtained by varying the thickness of the tubing.-Provides positive reinforcement and feedback for gauging results.-Available in xx-light, x-light, light, medium, heavy, x-heavy and xx-heavy. Options: -Available in several colors. Color/Finish: -Color-coded in proprietary Thera-Band colors increasing in difficulty.