ALL-ROUND: The 9 inch exercise ball is one of the essential Exercise Ball Accessories. This bender ball is a pilates ball for exercise that is different from other 9 inch pilates ball. The pilates ball 9 inch strengthens key muscles. The coregeous ball yoga enhances core health. The yoga ball small improves endurance flexibility. The gertie balls are used in rehabilitation strengthening. The mini yoga ball is used in toning exercise programs and relieve back pain and tension at work.