Professional resistance loop bands of different resistance levels. Red (2-15lbs): Lowest resistance for beigainer to warm-up, stretching and light strength training. Green (15-35lbs): Low resistance for warm-up, stretching and light strength training. Perfect for shoulder training and other high performance speed training. Black (20-70lbs):Light to medium resistance to mobility exercises and stretching. Well suited for high stretch training / stretching. Purple (35-85lbs): Moderate to severe resistance for moderate fitness exercises and strength training. Also suitable as medium support for pull-ups. Blue (65-175lbs): Heavy resistance for heavy weight training, strong support in pull-ups. Perfect for speed and agility training such as push ups, squats, bench presses and other exercises. Specification of Each Single Band Red (2-15lbs): 82 x 0.2 x 0.2 inch/1.8 oz/2-15 lbs Green (15-35lbs): 82 x 0.5 x 0.2 inch/3.9 oz/15-35 lbs Black (20-70lbs): 82 x 0.9 x 0.2 inch/6.7 oz/25-70 lbs Purple (35-85lbs): 81.9 x 1.3 x 0.2 inch/9.9 oz/35-85 lbs Blue (65-175lbs): 81.9 x 1.7 x 0.2 inch/138 oz /65-175 lbs