These 9 x 12 Self-Sealing Postal Approved Bags protect and keep direct mail pieces clearly visible. These postal approved mailers meet the requirements set by the United States Postal Service (USPS) for use on automation rate flat-size mail pieces for mailings effective February 1, 2007 and the specifications set in USPS T-3204 (Test Procedures for Automatable Polywrap). These postal poly mailers bags have high clarity, low density and are made from virgin resin. Custom Printing Available.