Rugby balls have traditionally been made using brown leather, but modern editions often use natural rubber or synthetic materials that are better able to withstand the elements. Either may be acceptable based on an individual league's rules. Polyester is used as backing material to hold the ball's oval shape. Additional material for grips and laminates may be used to enhance performance. An inflatable latex bladder is inserted inside the outer materials, with an accessible valve that allows it to be inflated to the regulated level. The ball is stitched together by hand with polyester thread that is coated with wax to strengthen the thread and make it more water-resistant.