A trademark used to identify a service rather than a product is sometimes called a service mark. They are frequently used by industrial standards bodies or certification companies to show "approval" of another product in some way. For example, Underwriters Laboratories holds a service mark on the phrase "UL Listed," and allows manufacturers of electrical equipment to use the service mark only if they have been approved by UL. This lets consumers identify products that meet quality criteria set by a company other than the manufacturer.