Minimum Weight: None
Maximum Weight: 70 pounds.
Required Marking: "Priority Mail."
All matter that is mailable by air transportation can be mailed as Priority Mail. Some things MUST be mailed as Priority Mail (or First-Class Mail), including:
If getting your mail there fast is your top priority, Priority Mail offers the best value. Priority Mail postage includes forwarding and return service. You can enhance the service, security, and convenience of Priority Mail by adding extra services such as USPS Tracking/Delivery Confirmation and Registered Mail. These services are available at retail Post Offices for a small fee. USPS Tracking/Delivery Confirmation is free of charge on Priority Mail when postage is paid for and printed online or through commercial payment options.
Priority Mail postage is determined by how far the mailpiece must travel to get to its destination: the farther it travels the more you pay in postage. The actual distance is measured by "zones." Zones range from zone 1 (local, close to you) to zone 8 (very far away from you). The farther the mail travels, the more zones it crosses, and the more postage you pay. You can access zone charts online. For some large, lightweight Priority Mail packages you will use dimensional weighting for postage if the package is going to zones 5-8.
The Postal Service offers special prices for Priority Mail Flat Rate Envelopes or boxes. Regardless of weight (up to 70 lbs.) or domestic destination, any amount of material that fits into a USPS-provided Priority Mail Flat Rate Envelope or box can be mailed for one low price. Priority Mail envelopes, boxes, and tubes are available for free from your local Post Office or on-line at www.usps.com.
Priority Mail parcels that weigh less than 20 pounds and measure more than 84 inches in combined length and girth are charged a "balloon price" (the price for a 20-pound parcel to that zone addressed for delivery to zones 1-4).
Parcels addressed for delivery to zones 5-8 that exceed 1 cubic foot (1,728 cubic inches) are charged postage based on the actual weight or the "dimensional weight" whichever is greater.