The weight limit is 4 pounds.
- Minimum length and height: 5–1/2 inches x 3–1/2 inches.
- Minimum depth (thickness): .007 inch.
- Maximum length: 24 inches.
- Maximum length, height, depth (thickness) combined: 36 inches.
- Minimum length: 4 inches.
- Minimum length plus twice the diameter combined: 6–3/4 inches.
- Maximum length: 36 inches.
- Maximum length plus twice the diameter combined: 42 inches.
Unenclosed cards exceeding the size limits for postcards are admissible at the First-Class Mail International rate if they do not exceed 4–3/4 inches x 9–1/4 inches.
A $0.17 per-piece surcharge is applied to a First-Class Mail International item if it has one or more of the following characteristics:
- Has any dimension that exceeds the acceptable standard dimension — i.e., if length exceeds 11–1/2 inches, or if height exceeds 6–1/8 inches, or if thickness exceeds 1/4 inch.
- Has an aspect ratio (length divided by height) of less than 1.3 or more than 2.5.
- Is polybagged, polywrapped, or enclosed in any plastic material.
- Has clasps, strings, buttons, or similar closure devices.
- Contains items such as pens, pencils, or loose keys or coins that cause the thickness of the mailpiece to be uneven.
- Is too rigid (does not bend easily when subjected to a transport belt tension of 40 pounds around an 11–inch diameter turn).
- For pieces more than 4–1/4 inches high or 6 inches long, the thickness is less than 0.009 inch.
- Has a delivery address parallel to the shorter dimension of the mailpiece.
- For self–mailers with a folded edge perpendicular to the address, the piece is not secured according to DMM 201.
- For booklet–type pieces, the bound edge (spine) is the shorter dimension of the piece or is at the top, regardless of the use of tabs, wafer seals, or other fasteners.