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Custom Mail Services
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MAILPIECE DESIGN

LETTERS
Letter size mail is mail that is 4 1/4 inches high or more than 6 inches long and must not be thinner than .007 inches thick. 

POSTCARDS
Postcards are simply just a single layer of cardstock, cut to size. The maximum size is 4 1/4 x 6 inches. Anything larger than this size will qualify for letter rates. 
LETTER
Minimum
Maximum
Length
5 inches
11.5 inches
Height
3.5 inches
6.125 inches
Thickness
.007 inches
.25 inch
Picture
POSTCARD
Minimum
Maximum
​Length
5 inches
6 inches
Height
3.5 inches
4.25 inches
Thickness
.007 inch
.016 inch
Picture
Picture



​Downloadable PDF:  Printable Letter-Size Mail Dimensional Standards Template. Note: Print actual size on an 11x14, legal size paper. 

Avoid glossy stock for letters and postcards on automated mailings. 

FLATS
Flats are larger mailpieces that exceed the maximum requirements for letters. Automation flats cannot weigh more than 13 oz. and must be rectangular. Thickness must not exceed 3/4 inches. 
FLAT
Minimum
Maximum
Length
11.5 inches
15 inches
Height
6.125 inches
12 inches
Thickness
.25 inch
.75 inch
Picture
The length of a flat piece is the longest dimension. The height is perpendicular to the length. 
​
Flats must be flexible and universally thick. If a piece cannot bend without breaking it is not considered a flat. If the piece has more than 1/4 inch variedness in thickness, it is not considered a flat. 

FOLDED MAILERS​
​Folded self mailers and booklets must be tabbed to prevent the open edges from causing delays in the high-speed automation process. It is important that when you are designing a folded mailer that the fold is on the bottom of the mailer such as seen in the graphic below. 
Picture
Picture
If you have any questions about mailpiece design, please contact one of our mail specialists. This will help ensure that your pieces are designed for automation so you may recieve maximum discounts and to avoid USPS surcharges. 
Custom Mail Services
7676 Reinhold Drive
Cincinnati, OH 45237

(513) 821-7363 * phone
(513) 821-7370 * fax

Hours of Operation:
8:30 AM - 5:00 PM Monday thru Friday