Food & Agr. Code, § 61935

(a) Class 4a comprises all market milk, market skim milk, or market cream used in the manufacture of butter, dried milk, dried skim milk, nonfat dry milk solids, defatted milk solids, dried buttermilk, and all market milk, market skim milk, or market cream which is supplied to consumers as condensed milk, condensed skim milk, evaporated skim milk, evaporated cream or clotted cream, or evaporated milk, and any milk products which are UHT products, as defined in Chapter 9 (commencing with Section 39701) of Part 3 of Division 15, or ultrapasteurized, and sold for use outside of the 48 contiguous states in the United States, or yogurt, soft fresh cheese (fromage frais), uncreamed, creamed, or partially creamed cottage cheese, sour cream, sour half-and-half, or light sour cream which is sold for use outside the boundaries of the United States, or any product for which no definition and standards are prescribed in Division 15 (commencing with Section 32501), except the products defined in paragraph (2) of subdivision (a) of Section 61932.

(b) Class 4b comprises all market milk, market skim milk, or market cream used in the manufacture of cheese other than cottage cheese.