Priority Mail is used for documents, gifts, merchandise, and any mailable item weighing 70 pounds or less. The maximum size is 108 inches or less in combined length plus girth (distance around the thickest part). Mark each package "Priority Mail" in the postage area when you are not using USPS produced Priority Mail envelope or box.
Priority Mail service offers 1 day, 2 day, or 3 day service to most domestic destinations. Priority Mail envelopes and boxes are available at many Post Offices and can be ordered online at USPS.com/store. This 1-3 day service includes tracking and merchandise insurance up to $50. Additional merchandise insurance up to $5,000 may be purchased for a fee.
Parcels addressed for delivery to zones 1-4 (including local) that weigh less than 20 pounds and measure more than 84 inches but not more than 108 inches in combined length plus girth (distance around the thickest part) are charged the 20-pound Priority Mail zoned price.
Parcels addressed for delivery to zones 5-8 that exceed 1 cubic foot (1,728 cubic inches) are charged based on the actual weight or the dimensional weight, whichever is greater.