Red - XX-Light - ½" Wide
Primarily used for adding resistance to stretching exercises. Resistance is 5 - 35 pounds.

Purple - X-Light - 1 1/8" wide
Good choice as a general use band and a specifically for adding resistance to people under 140 pounds during walks high knees or sprints. Resistance is 25 - 80 pounds.

Green - Light - 1 ¾" wide
This band is also a good size for general use and for adding resistance to people from 140 to 200 pounds for body movements. Good choice for pull up training. Resistance is 50 - 120 pounds.