|Size||First Class Rate|
|Postcards (5"x3.5" to 6"x4.25")||$0.267|
|Letter-size 3.5oz or less||$0.407|
|Flats 1oz or less||$0.615|
|Letters 3.5oz or less||$0.271||$0.280|
|Flats 4.0oz or less||$0.515||$0.539|
Your mail piece is a "Letter" if it falls within these dimensions and weight.
(Certain pieces heavier than 3.3 oz are subject to being prepared as letters but paid as a flat)
Your mail piece is a "Flat" if it exceeds one of the letter size dimensions and does not exceed the maximum flat dimensions.
Exceptions to the minimum size: Every-Door direct mail pieces can have a length of 10 1/2 inches.
Flats cannot be too rigid and must be uniformly thick (within 1/4 inch).