On Apr 6, 8:26 am, David Harmon wrote:
What's the largest that will fit in a flat rate shipping box?

USPS Flat rate boxes:

11" x 8.5" x 5.5" $8.95 domestic
13.625" x 11.875" x 3.375" $8.95 domestic

And the new size
12" x 12" x 5.5" $12.95

http://www.usps.com/shipping/flatrate.htm