ProsourceFit Weighted Toning Exercise Balls for Pilates Balance, strength and stability training – unstable sand filling in these Pilates toning balls force deeper muscle Activation engagement during exercises for a stronger and leaner physiqueVersatile utility – weighted exercise ball is suitable for all fitness levels and ideal for Pilates, strength training, yoga or physical therapy exercisesErgonomic design – Unlike traditional dumbbells, The Mini workout ball is curved to fit in the palm of your hands to avoid wrist and arm pain during upper or Lower body exercises