FYI, I just paid a quick visit to the US Postal Service web site. If we send 5X7s instead of postcards, the postage will be 37 cents as opposed to 23 if sent to a US address. For overseas, it looks like the difference in postage will also be small. A postcard is not smaller than 3.5"X5" and no larger than 4.25X6. I hope that this helps.