9" x 5/8" Green Xercise Band is great for ankle and knee exercises within the average fitness level. 9" x 1½" Orange Xercise Band is great for ankle and knee exercises within the strong individual or athletic training levels. 9" x 2" Purple Xercise Band is great for ankle and knee exercises within the strong individual or athletic training levels. 9" x 1" Blue Xercise Band is great for ankle and knee exercises within the intense strength training level. 9" x 3/8" Yellow Xercise Band is great for ankle and knee exercises within the beginner and senior fitness levels. 9" x 3/4" Red Xercise Band is great for ankle and knee exercises within the above average fitness level.