Harvey balls are round ideograms used for visual communication of qualitative information. They are commonly used in comparison tables to indicate the degree to which a particular item meets a particular criterion. For example, in a comparison of products, information such as price or weight can be conveyed numerically, and binary information such as the existence or lack of a feature can be conveyed with a check mark; however, information such as "quality" or "safety" or "taste" is often difficult to summarize in a manner allowing easy comparison – thus, Harvey balls are used.