5pcs stackable exercise bands have different resistance levels: Yellow(10 lbs), Blue(20 lbs), Red(30 lbs), Green(40 lbs), Black(50 lbs). They can be used alone or stacked in any combination of intensity from 10 lbs to 150 lbs. Great for toning your quads, glutes, buttocks, abs, biceps, triceps, legs and knees.