You control the motion and weight with the Tanker 5-25 by simply filling it with water to increase the weight. This dual-handle fitness ball is one of the best multipurpose training tools around. Train your deep core muscles to improve strength, balance, body mechanics and to prevent injuries. Build a strong platform for total body health with toe reaches, lateral twists, chops, and seated rotational exercises with the Tanker 5-25. Key features: