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Flat (USPS)
From Wikipedia, the free encyclopedia
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The United States Postal Service uses the words "flats" and "nonletters" interchangeably to refer to large envelopes, newsletters, and magazines.
![]() | The examples and perspective in this article may not represent a worldwide view of the subject. (March 2025) |

Size restrictions
To fit the definition a flat must:
- Have one dimension that is greater than 6-1/8 inches high OR 11-½ inches long (the side parallel to the address as read) OR ¼ inch thick.
- Be no more than 12 inches high x 15 inches long x ¾ inch thick.
- Weigh no more than 13 ounces.
Furthermore, the item must be somewhat bendable: see the USPS Domestic Mail Manual for exact details. This general rule does not apply to: Automation rate flats and Standard Mail Enhanced Carrier Route flats.
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Postage
The maximum size for a flat provides enough room to enclose much material. An issue, however, is that the higher the weight the higher the postage, especially for First-Class Mail.
External links and references
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