The boxes are provided by USPS for free, and if your shipment is going to Zones 1-4, you'll find that this option is usually less expensive than Flat Rate Boxes. Priority Mail Medium Flat Rate Box ...

By the time you buy the right envelope and add insurance, you may be better off going with a USPS Priority Mail Flat Rate Envelope, which costs $9.65. The postal service will provide a free ...

Sending your mail or packages under the appropriate U.S. Postal Service (USPS ... with Priority Mail labels, stickers, envelopes and boxes at no extra charge. The 2-pound flat-rate envelope ...