The Iron Body Fitness toning balls are ideal for pilates, yoga, and upper body weight training and assist in increasing intensity and improving core stability. They also help to sculpt and tone muscles without adding bulk compared to traditional medicine ball workouts.IBF Iron Body Fitness toning balls are ideal for a variety of pilates, aerobics and stretching exercises to improve your core strength, muscle tone and flexibility. Increase the challenge of your yoga and pilates training with this lighter-weight alternative to traditional medicine balls. These sand-filled PVC toning balls have a soft, easy-to-grip surface, and are designed to fit comfortably in the palm of your hand.Includes 2 x 4 lb. (1.81 kg) toning balls.