Adjustable Weight: Aqua bag reacts to your every movement, every repitition is different, Its excellent Challenge for muscles and motor to give different action to control each time. promotes muscle growth for the fitness lover, Good Balance Training Super Comfortable and Secure: Aqua Bag has a soft and smooth surface to reduce damages from injuries during workout. While you exercise with this sandbag alternative, You will hear the sound of clear water, like a splendid music. so relaxed