 
    | Size | First Class Rate | 
|---|---|
| Postcards (5"x3.5" to 9"x6") | $0.443 | 
| Letter-size 3.5oz or less | $0.636 | 
| Flats 1oz or less | $1.256 | 
| Flats 1-2oz | $1.526 | 
| Size | Standard Mail | Non-profit | 
|---|---|---|
| Letters 3.5oz or less | $0.404 | $0.210 | 
| Flats 4.0oz or less | $1.011 | $0.744 | 
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).
