Activa Small Balls and Medium promote blood circulation, reduce stress and relax muscles. They are usually included in preventive and rehabilitation programs. All Activa balls can be easily inflated and deflated to vary the intensity of the massage or self-massage. These simple massage and self-massage tools have been specifically designed and manufactured to provide pleasant feelings of well-being. The Activa Medium ball can be inflated to a diameter of 9 to 12 cm.