(a) SI metric declarations of net quantity of contents of any consumer commodity may contain only decimal fractions. Other declarations of net quantity of contents may contain common or decimal fractions. A common fraction shall be in terms of halves, quarters, eighths, sixteenths, or thirty-seconds; except that:

(1) If there exists a firmly established general consumer usage and trade custom of employing different common fractions in the net quantity declaration of a particular commodity, they may be employed, and

(2) If linear measurements are required in terms of yards or feet, common fractions may be in terms of thirds. A common fraction shall be reduced to its lowest terms; a decimal fraction shall not be carried out to more than three places.

(b) If a statement includes small fractions, smaller variations in the actual size or weight of the commodity will be permitted as provided in §500.25, than in cases where the larger fractions or whole numbers are used.