A "hollow ball" is a spherical object that has an empty space or cavity inside. This design can be found in various materials, such as rubber, plastic, or metal, and is often used in toys, sports equipment, and scientific applications. The hollow structure allows for lighter weight and can enhance performance in certain activities, like soccer or basketball. In addition to recreational uses, hollow balls are also utilized in engineering and manufacturing. For example, they can serve as containers for gases or liquids, or as components in machinery. Their unique shape and structure make them versatile in both everyday items and specialized applications.