USPS Maximums & Minimums

Letter: 6 1/8 x 10 1/2
            3 1/2 x 5

Post Card: 4 1/4 x 6
                  3 1/2 x 5

Font Size: 18 pt max, 8 pt min
                 All caps preferred

Font Type: San Serif, no kearning
                  (examples: Helvetica, Geneva)

Font Style: Plain