Flats requirements are changing March 29, 2009. For more information click on the below links to the following USPS Publications.

For flat size mail at Automation and / Presorted First Class click here for a quick fact sheet.

For flat size mail at Media Mail, Library Mail, or BPM click here for a quick fact sheet.

For flat size mail Peridicals click here for a quick fact sheet.

For flat size mail Standard Mail rates click here for a quick fact sheet.

For the May 7, 2008 Federal Register notice with detailed information click here.