U.S. Grade B Small; U.S. Grade B Medium; U.S. Grade B Medium to Large; U.S. Grade B Large.

Potatoes of each of these grades shall meet the requirements for U.S. Grade A Small; U.S. Grade A Medium; U.S. Grade A Medium to Large; and U.S. Grade A Large, except for the increased tolerance for defects specified below. (See § 51.1577.) (a) Tolerances. Incident to proper grading and handling, except for the tolerance for size, not more than a total of 20 percent, by weight, of the potaotes in any lot may fail to meet the requirements of the grade, but not more than 5 percent shall be allowed for potatoes which are seriously damaged by any cause, including not more than 1 percent for potatoes affected by soft rot or wet breakdown. (See § 51.1579.)