Impact Your Bottom Line
• At least 31⁄2˝ high x 5˝ long x .007˝ thick.
• No more than 6 1⁄8˝ high x 111⁄2˝ long x 1⁄4˝ thick.
Flats (Non-letter mail)
This category of mail is the Postal Service's catch-all for just about any non-letter and non-card mailings—excluding parcels. The following characteristics define a flat mailing:
• Has one dimension that is greater than 61⁄8˝ high OR 111⁄2 ˝ long OR 1⁄4˝ thick.
• Is no more than 12˝ high x 15˝ long x 3⁄4˝ thick.
• Caution: The more you stuff into a flat-size mailing, the more it weighs. For flats exceeding the limit of 3.3 ounces, mailers pay the single piece rate plus a pound rate.