Congressional third-class mass mailings are letter-size or flat size. The processing category is
determined by the size and the weight of the mailpiece.
Letter-Size Mail Dimensions: | Min | Max |
Height: | 3 1/2" | 6 1/8" |
Length: | 5" | 11 1/2" |
Thickness: | .007" | 1/4" |
Flats are mail that exceeds one or more of the letter-size dimensions.
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