The new Priority Mail Large Flat-Rate Box (12" x 12" x 5½") can be used for both domestic and international shipments. This extends the flat-rate price and ease-of-use benefits to international shippers. There is also a 5 percent online discount.
There will be a special version of the box for the military, with a $2 discount, if shipped to an Army Post Office or Fleet Post Office (APO/FPO) address.
Read more here.