Body Jewellery. Clip-in add-on's are balls or weights which are used to secure a ball closure ring shut. They have one dimple on either side of the ball which the sides of the ring sit in, this holds the ball in place. The size of the add-on should match the gap in the ball closure ring. It is best to measure the ball or ring that you have already to ensure you get the correct size. For more information about sizing please read our guide or contact us for advice about body jewellery.