Andy, I pulled this from our new IMM(International Mail Manual).

Nonmachinable Surcharge:
An additional $0.13 is required for items weighing 1 ounce or less with any of the following criteria:

A. Square letters.
B. The height exceeds 6-1/8 inches, or length exceeds 11-1/2 inches, or thickness exceeds 1/4 inch.
C. The length divided by height is less than 1.3 or more than 2.5 (length is the dimension parallel to the address).
D. It has clasps, strings, buttons, or similar closure devices.
E. It is too rigid or contains items such as pens that cause the thickness of the mailpiece to be uneven.
F. It has an address parallel to the shorter dimension of the mailpiece.

The whole reason for this increase is crazy anyway, as all the USPS is doing is building a $3B "slush fund" that Congress voted into law. Could I get you to put my mortgage payment for the new few years down on the fact that the money gets deferred to some politicians pet project?