1. Using special ETDM transparent rubber for the Bladder & Surface. 2. The LED and battery is replaceable。 3. The unique transparent surface to allow us discover the mystery winding and ball structure. 4. Two LEDs are spread the light equally and attractive. 5. Official weight and size to keep training and have fun all night long. 6. Automatic light up with every kick. 7. Each kick will make the light turn on for 1 minute. 8. The battery will last for 40 hours.