LETTERS
The maximum weight for a First-Class letter is 3.5 oz. and 3 oz. for a booklet.
The maximum weight for a Marketing Mail letter is 4 oz. and 3 oz. for a booklet.
Letter-size mail (not booklets) that weigh between 3 and 3.5 oz. is considered
“Heavy Letter Mail” and must be mailed in an envelope.
In addition, “Heavy Letter Mail” may not include stiff enclosures.
Pieces more than 6” long and 4 1/4” high must be at least .009” thick to qualify
for automation rates.
Must meet aspect ratio of 1.3 – 2.5 (width divided by height).
Cannot be too rigid. Must pass droop test.
Minimum
Minimum
Maximum
Maximum
Length
Length
5"
5"
11 1/2"
11 1/2"
Height
Height
3 1/2"
3 1/2"
6 1/8"
6 1/8"
Thickness
Thickness
.007"
.007"
1/4"
1/4"
5" min.
11 1/2" max.
3 1/2" min.
6 1/8" max.