§ 3207. 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 that class of mail receiving high priority in handling and delivery, 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 Documents.
• (b) A penalty mail article which is—
  • (1) over 4 pounds in weight;
  • (2) not in excess of the weight and size prescribed for mail matter; and
  • (3) otherwise mailable;