16 CFR 303.29: Labeling of pairs or products containing two or more units.

(a) Where a textile fiber product consists of two or more parts, units, or items of different fiber content, a separate label containing the required information shall be affixed to each of such parts, units or items showing the required information as to such part, unit, or item: Provided, That where such parts, units, or items are marketed or handled as a single product or ensemble and are sold and delivered to the ultimate consumer as a single product or ensemble, the required information may be set out on a single label in such a manner as to separately show the fiber composition of each part, unit, or item.

(b) Where garments, wearing apparel, or other textile fiber products are marketed or handled in pairs or ensembles of the same fiber content, only one unit of the pair or ensemble need be labeled with the required information when sold and delivered to the ultimate consumer.