Limit of weight of penalty mail; postage on overweight matter

§ 4158. Limit of weight of penalty mail; postage on overweight matter (a) Penalty mail is restricted to articles not in excess of the weight and size prescribed for first class mail, except— (1) stamped paper and supplies sold or used by the postal service; and (2) books and documents published or circulated by order of Congress when mailed by the Superintendent of Public Documents. (b) A penalty mail article which is— (1) over four pounds in weight, (2) not in excess of the weight and size prescribed for fourth class matter, and (3) otherwise mailable, is mailable at fourth class rates even though it may include written matter and may be sealed. The postage on such an article is payable in the manner prescribed by the Postmaster General.