29 CFR § 779.327 - Wholesale sales.

A wholesale sale, of course, is not recognized as a retail sale. If an establishment derives more than 25 percent of its annual dollar volume from sales made at wholesale, it clearly cannot qualify as a retail and service establishment. It must be remembered, however, that what is a retail sale for purposes of a sales tax law is not necessarily a retail sale for purposes of the statutory definition of the term “retail or service establishment”. Similarly, a showing that sales of goods or services are not wholesale or are made to the ultimate consumer and are not for resale does not necessarily prove that such sales or services are recognized in the particular industry as retail. (Wirtz v. Steepleton General Tire Co., 388 U.S. 190.)