The US Postal Service has changed the requirements for Folded Self-mailer (FSM) automation mailings starting in 2013 and they may affect your design and print production.
The changes go into effect January 5, 2013 and include new size requirements and new folding, tabbing and gluing requirements. The specs for these changes are included below and more information can be found in this pdf: FSM Reference Document
Height: A minimum of 3 1/2 inches and a maximum of 6 inches.
Length: A minimum of 5 inches and a maximum of 10 1/2 inches.
Thickness: A minimum of 0.007 inch; (0.009 inch if the height exceeds 4 1/4 inches or if the length exceeds 6 inches); the maximum thickness is 1/4 inch.
Maximum Weight: 3 ounces.
Shape: Rectangular, with four square corners and parallel opposite sides.
Aspect ratio: Within 1.3 to 2.5.